There is nothing wrong with using the expression “by chance”
Question

 
Is it permissible to use the expression “by chance”, such as saying, “I went to the market and I met So and so by chance”?
 Is this phrase “by chance” haram or does it constitute shirk (associating others with Allah)? What should I say instead of this? Please advise me, may Allah reward you with good.
Praise be to Allah.There is nothing wrong with using the phrase “by chance,” because what the speaker means is that he met that person without a prior agreement to meet, and without intending to do so; he does not mean that this meeting happened without the decree of Allah. 
The use of this expression (sudfatan in Arabic) is mentioned in some ahaadeeth, such as that narrated by Muslim (2144) from Anas who said: I set out with him (i.e., with ‘Abd-Allah ibn Abi Talhah) to go to the Messenger of Allah (peace and blessings of Allah be upon him), and we met him by chance and he was carrying a branding iron… 
Abu Dawood (142) narrated that Laqeet ibn Sabrah said: I came among the delegation of Banu’l-Muntafiq to the Messenger of Allah (peace and blessings of Allah be upon him). When we came to the Messenger of Allah (peace and blessings of Allah be upon him) it so happened that we did not find him in his house but by chance ‘Aa’ishah the Mother of the Believers was there…. This hadeeth was classed as saheeh by al-Albaani in Saheeh Abi Dawood. 
It says in Fatawa al-Lajnah al-Daa’imah (3/393): 
The expression used by many people, “I met So and so by chance” etc is not haram and does not constitute shirk, because what is meant is meeting him without a prior appointment or agreement to meet, for example, and there is nothing wrong with this meaning. 
Shaykh Ibn ‘Uthaymeen was asked: What is your opinion on using the expression “by chance”? 
He replied: 
We think that there is nothing wrong with this expression. This is a customary expression which is mentioned in several ahaadeeth: We met the Messenger of Allah (peace and blessings of Allah be upon him) by chance, etc. 
With regard to people’s actions, things do happen by chance, because people have no knowledge of the Unseen and a thing may happen without a person realizing it or doing the things that lead to it or expecting it. But with regard to the actions of Allah, this is not the case, for everything is known to Allah and everything is decreed by Him. With regard to Him nothing ever happens by chance, but with regard to you and me, we may meet without prior arrangement and without realizing or planning it. This is what we call chance, and there is nothing wrong with that. But with regard to the actions of Allah, this word cannot be used. 
Fatawa al-Shaykh Ibn ‘Uthaymeen, 3/117 
And Allah knows best.