Is it permissible to say “Let Allah work through you and trust Him”
Question

I read on a website the words “Let Allah work through you and trust Him, for the whole universe is running in the most beautiful way, so why would He be unable to take care of you? Why should you worry or fear for yourself? Roses do not worry and neither do stars.” Is it permissible to speak in this way?
Praise be to Allah.Firstly: trusting in Allah and relying on Him is something that is required according to Islamic teachings
Trusting in Allah, depending on Him and relying on Him is something that is required according to Islamic teachings, as Allah, may He be exalted, says (interpretation of the meaning):
{To Allah belongs all that is unseen in the heavens and on earth, and to Him all things will return. So worship Him [alone] and put your trust in Him, for your Lord is not unaware of what you do} [Hud 11:123]
{Put your trust in the Ever-Living Who never dies, and glorify and praise Him. Your Lord is sufficiently aware of the sins of His slaves} [Al-Furqan 25:58]
{Put your trust in Allah, for sufficient is Allah as a disposer of affairs} [Al-Ahzab 33:3].
Allah, may He be exalted, is the Disposer of affairs Who is taking care of His slaves; He is the Provider who provides for them; He is the Most Merciful and no one is more merciful to them than Him; He is the Sustainer by Whom everything is sustained. Whoever puts his trust in Allah, He will suffice him; whoever turns to Him, He will guide him; whoever believes in Him, He will provide for him; whoever relies on Him, He will not let him down.
Allah, may He be glorified, says (interpretation of the meaning):
{Whoever fears Allah, He will grant him a way out [from difficulty],
and will provide for him from where he does not expect. Whoever puts his trust in Allah, He will suffice him. Allah will surely attain His purpose. Allah has set a measure [and appointed term] for all things} [Al-Talaq 65:2-3].
Ahmad (205) narrated from ‘Umar ibn al-Khattab that he heard the Prophet of Allah (blessings and peace of Allah be upon him) say: “If you were to put your trust in Allah as you should, you would be given provision like the birds: they go out hungry in the morning and come back with full bellies in the evening.”
As the entire universe is running by the might of Allah and is under His control, how could Allah not be able to look after His slaves’ affairs? As Allah has guaranteed to provide and care for His slaves, then why worry?
Allah, may He be exalted, says (interpretation of the meaning):
{There is no creature that lives on the earth but its sustenance is guaranteed by Allah. He knows its dwelling place and its resting place; all is [inscribed] in a clear record} [Hud 11:6].
Whatever befalls a person of exhaustion, fatigue or worry, Allah will expiate his sins thereby, and whatever happens was already decreed before the individual was created, so what is the benefit of feeling depressed or troubled?
Allah, may He be exalted, says (interpretation of the meaning):
{No calamity befalls the earth or your own selves but it is already written in a Book before We make it happen. Verily, that is easy for Allah.
[Know this] so that you do not grieve for what passes you by, nor exult over what He gives you, for Allah does not love anyone who is conceited and boastful} [al-Hadid 57:22-23].
The Prophet (blessings and peace of Allah be upon him) said: “No fatigue, constant pain, worry, grief, harm or distress befalls a believer, not even a thorn that pricks him, but Allah will expiate some of his sins thereby.” Narrated by al-Bukhari (5642) and Muslim (2573).
Secondly: what is required of the individual is to observe proper etiquette when addressing the Lord of the Worlds
The words mentioned are correct, as they invite people to trust and rely on Allah, and not be worried or distressed. But the way the phrase “Let Allah work through you” is worded is not correct and is not appropriate to the majesty of Allah, may He be glorified and exalted. For Allah does not need permission from anyone and He does not act through anyone – exalted and sanctified be Allah. For no one could ward off His bounty or prevent it from reaching anyone. Allah, may He be exalted, says (interpretation of the meaning):
{Whatever Allah opens up for people of His mercy, none can withhold it, and whatever He withholds, none can grant it thereafter. And He is the Almighty, the Most Wise} [Fatir 35:2]
{If Allah afflicts you with harm, none can remove it but He; if He wills some good for you, none can avert His bounty, which He bestows upon whomever He will among His slaves. And He is the Oft-Forgiving, Most Merciful} [Yunus 10:107].
One of the supplications and adhkar of the Prophet (blessings and peace of Allah be upon him), when he had finished the obligatory prayer, was to say: “La ilaha illa Allah wahdahu laa sharika lah, lahu al-mulk wa lahu’l-hamd wa huwa ‘ala kulli shay’in qadir. Allahumma la mani‘a lima a‘tayta wa la mu‘tiya lima mana‘ta wa la yanfa‘u dha’l-jaddi minka al-jadd (There is no god worthy of worship except Allah alone, with no partner or associate; His is the Dominion, to Him be praise, and He has power over all things. O Allah, none can withhold what You give and none can give what You withhold, and the good fortune of any fortunate person is to no avail against You.)”
Narrated by al-Bukhari (6615) and Muslim (593) from al-Mughirah ibn Shu‘bah.
Imam al-Bukhari included this hadith in a chapter in his Sahih entitled Chapter: None can withhold what Allah gives.
In Sahih Muslim (477) it is narrated that Abu Sa‘id al-Khudri said: When the Messenger of Allah (blessings and peace of Allah be upon him) raised his head after bowing, he would say: “Our Lord, to You be praise, filling the heavens and the earth, and filling whatever You will besides that. You are worthy of praise and glorification; this is the truest thing that a slave can say, and all of us are Your slaves. O Allah, none can withhold what You give and none can give what You withhold, and the good fortune of any fortunate person is to no avail against You.”
Even though the one who spoke these words meant nothing but good, what is required is to adhere to proper etiquette when addressing the Lord of the Worlds and speaking of Him, and we must be careful to speak of Allah in words that are appropriate to His greatness, majesty and affection.
The individual is the doer of his deeds, by his choice and will, but Allah is the Creator of him and his will. He knows what he will do, and He, may He be glorified, helps and guides whomever He wills of His slaves; if they are deprived of His help and guidance, they will go astray. Hence the people of Paradise will say (interpretation of the meaning):
{Praise be to Allah Who has guided us to this, for we would never have been guided if Allah had not guided us} [Al-A‘raf 7:43].
We ask Allah to guide us and help us to do that which He loves and which pleases Him.
And Allah knows best.