"The number of dust on the earth could be counted..." In the video documentary Go Beyond Samsara - Part 2, it mentions that Buddha had said:


  "The number of dust on the earth could be counted, but the number of
  beings that had been one's parents is in no case calculable"


I'd like to see this in its fuller context. Where in the pali canon or other scriptures did the buddha say this and can you point me to it?

I have researched and I can only find similar biblical references like here.

Note: The video link above will play at the very moment in question.
THe puthujjanas who created Mahayana and vajrayana love to claim that people you see around you could have been your parents or loved ones in a previous life.
From this, they embarrass themselves even more by inferring that ''therefore you must be nice to them'', so that they build their humanist ethic and feel good about themselves. As usual they confuse the sila of the dhama with humanism.

Their confusion stems from their confusion of the dependent origination of the 5 aggregates with the dependent origination that they invented which they called ''inter-being'' which is just the eastern humanism where people depend on each others.
Those puthujjanas prefer to care more about the thousands little objects and humans they see each day and slap the words sunnata and dependent origination on it Whereas the claim of the buddha is precisely that instead of caring about those objects, what matters is to see how conditioned the 5 aggregates are.
Puthujjanas who do not cling to mental masturbation already know that objects and livelihood are conditioned, and this knowledge doe snot get them enlightened, but a few intellectuals pass this dull, bland, common knowledge as being awaken. 

The philosophers are the textbook case of overthinking, they focus on a few words and they build a new system around it, a new semantics, a new doctrine. 
Their story begins with the a famous claim that what is anicca is dukkha, what is dukkha is anatta. THen a natural question by Puthujjanas is ''why are things anatta'' and of course, the answer is that ''things are anatta because it is the way they are''. IT is a disappointing answer, because it is a stupid question in the first place.

But of course, for the Puthujjanas who are intellectuals, this answer is not intellectual enough. No, what matter to those Puthujjanas is to put another ''...because XYZ'' after ''because they are anatta'': They claim that things are anatta because they are sunyata. They picked the word sunyataand blew it out of proportion, by using it on their deep craving to find an essence in things.
When those Puthujjanas run out of ideas to intellectualize further their views, they stop and claim that the last bit of their sequence of ideas is in fact how reality is, so it goes


  idea A because idea B, idea B because idea C, .... , idea X because
  idea Y, idea Y because idea Z, and idea Z because reality is Z
  (expressed by idea Z). Which means ''Y because Z because it is the way
  it is, end of the story''


Now it turns out that the story imagined by those Puthujjanas does indeed stop  at sunyata:  things are sunyata because things are sunyata, because that is what things are, because it is the way things are.
And of course, those people love to feel smart for applying their fantasy to the most attractive word there is:


  Nibbana (the Unconditioned) is anatta because nibanna is sunyata. And
  Why is nibanna sunyata? Nibanna is sunyata because nibanna is sunyata.


With the crown of their speculations being the fantasy that:


  sunyata itself is sunyata


THis jewel of theirs is precisely what neuters their speculations. It puts a stop to the chain of ''because XYZ'' and adds nothing to the story. 
Thus,  It is easy for those puthujjanas to claim that ''


  If dependent origination is true, then my attainment of enlightenment is mutually dependent on the attainment of all other beings.


So their craving for slapping sunyata eveyrwhere is utterly useless. They had an extra word and they stop here. It is already bad to intellectualize, but intellectualizing further by adding a useless word is embarrassing. But at least they obtain what they craved all along, fantasizing a true nature of ''the self'', as if things had a true nature and a not so true nature.
Later on, they cannot help themselves from claiming that their intellectualization is the dhamma and even more embarrassing, that it is a better dhama than the one from what they call the ''pali canon'' today, 

But the intellectuals do not stop here. Those puthujjanas crave so much speculating and basing their life on their fantasies that they picked another word and blew it out of proportion by mixing it with their favorite topic: craving to attribute an essence or a true nature to things that they perceive.
Their new and equally  toxic fairy tale is about applying what they read about dependent origination to their craving for true nature of things like the external object.

THe dependent origination is and always will be about the conditions for the birth of an aggregate and the condition for the death of an aggregate. Dependent origination is never ever about the condition of the birth of the objects that Puthujjanas love to cling to and which live ''in reality'' like they say.
On the contrary, if there is ONE thing that the buddha does NOT focus on is precisely those stuff of what Puthujjanas call ''objective reality''. It is utterly useless and never conductive to nirvana.

In fact, Puthujjanas know very well that the objects they crave are fabricated. Puthujjanas know that the meal they cook is sunyata.Puthujjanas know very well that their car is sunyata, that clouds are sunyata. THey know that when they change the summer tires on their car, to put a winter tires, the drive-ability of the car changes a lot, that the fuel consumption changes a lot, to the point of driving a totally different car. They know that when they change the gearbox or the engine, the car no longer behaves like the car before to the point of being a different car. And knowing that all those objects are sunyata does not get them to stop being Puthujjanas, does not stop the cravings they have for the objects nor the craving they have to find the ''real nature'' of things. Knowing that a carrot is fabricated is not reaching nibanna.
The dependent origination is never ever about the condition of the birth of a carrot nor the about the condition of the death of a carrot.

THe buddha and the bikkhus used the analogy of the fabricated chariot and the scent of the flower, the sound of a lute https://www.accesstoinsight.org/tipitaka/sn/sn35/sn35.205.than.html
 to talk about the 5 aggregates precisely because Puthujjanas know those objects and that the all those objects are fabricated. The fabrication of the chariot is not new to Puthujjanas. What is new to Puthujjanas is that the 5 aggregates are fabricated, just like their car is fabricated. This is the claim which is amazing.

Claiming that a carrot is sunyata is the most bland, common, vulgar claim for the Puthujjanas who do not build much views beyond sakkya-ditthi.
On the contrary, for the toxic Puthujjanas who love to pat themselves on the back for intellectualizing even more the few bits they read about the dhamma, the claim that a carrot is sunyata  is amazing, is deep, is the most profound revelation that there is.
The intellectuals find amazing what the Puthujjanas who do not create much views beyond sakkya ditthi do not find amazing at all. 

it's like living in a builidng with many floors. Puthujjanas who know that the objects they fabricate are fabricated live on the floor 0, and the one who cannot help themselves from intellectualizing live on floor 100.
Puthujjanas who love to live up their dreams high at the floor 100 have completely forgotten that floor 0 exist. Then they pat themselves on the back for constructing a whole fairy tale leading them to discover that floor 0 have always existed. THen , the buddha lives at floor -1  and tells the Puthujjanas at floor 0 that there is a floor below them.

But it gets worst for those Puthujjanas clinging to rationalize that they experience. Because they exhaust themselves by struggling to fight their  views, they run out of energy when it is time to kill the lusts for the various 5 senses.
In fact, the most toxic Puthujjanas are not even interested in restraining their actions and prefer to claim that they already are awaken, because they delude themselves even more by creating the view that all that matters to reach nibanna is to have good intentions, so they go on carrying on their actions of Puthujjanas while building the fantasy that they have good intention while they are doing them. In order to express this new  view, that they love to pass as deep and pragmatic, They create the most moronic claim ever uttered by a deluded Puthujjana :


  ''Samsara is only nirvana seen from a place of confusion'' or  "Before Enlightenment chop wood, carry water. After enlightenment chop wood, carry water".


What is the meaning of the Zen quote: &quot;Before Enlightenment chop wood, carry water. After enlightenment chop wood, carry water&quot;?

They really feel smart and deep when they say that.
On the contrary, the Puthujjanas who already know that carrots are sunyata have zero need to kill the speculations created by the toxic Puthujjanas. The Puthujjanas who do not build much views beyond sakkyaditthi struggle the least to reach nibbanna. Those Puthujjanas are easy to talk to and the easiest way to make them ''understand'' that the 5 aggregates are conditioned is to talk to them and create analogies from their daily life with all those objects that they work so hard to fabricate and service. Those non-philosopers  Puthujjanas do not confuse samsara with nirvana. Those Puthujjanas do not get awaken by seeing that cars are fabricated, they get awaken by seeing that the 5 aggregates are conditioned which leads to the death of the lusts for the aggregates which kills the aggregates at least at parinibbanna, if not at nibanna.

The goal is not to see that a carrot is sunyata, nor that to see that a car is sunyata , nor that a sound is sunyata . The goal is only to see that the aggregates are sunyata which leads to see that  in the ''sound there is only the sound'' (an no other stuff like lust), to cognize the earth element as only the earth element, contrary to puthujjanas who cognize the earth element as earth element+sakkaya ditthi and later on, speculate on this sakkayaditthi and turn that into their numerous mistaken:


  The Blessed One said: "There is the case, monks, where an uninstructed
  run-of-the-mill person — who has no regard for noble ones, is not
  well-versed or disciplined in their Dhamma; who has no regard for men
  of integrity, is not well-versed or disciplined in their Dhamma —
  perceives earth as earth. Perceiving earth as earth, he conceives
  [things] about earth, he conceives [things] in earth, he conceives
  [things] coming out of earth, he conceives earth as 'mine,' he
  delights in earth. Why is that? Because he has not comprehended it, I
  tell you.


https://www.accesstoinsight.org/tipitaka/mn/mn.001.than.html