Allah's Promise in the Qur'an

Rizq, in general, lies absolutely in the hands of Allah (swt), in the most absolute of terms. He says, in one particular āyah:

So many a moving, living creature is there in the universe that Allah (swt) has created, that carries not its own provision — they do not produce their own rizq. Allah (swt) provides for them, for the creature and for the human being besides, and He is the All-Hearer, the All-Knower. And Allah (swt) says also, in Sūrat Hūd:

There is not a single moving creature that moves on earth — from the very littlest of bugs to a blind spider, living three or four storeys down in a dark basement, that sets up its net, so that a fly finds its way through the smallest of holes, comes inside, and sticks itself nicely to the web — whose rizq is not guaranteed; and the blind spider goes and eats it. Who is it that guarantees that rizq? And beneath the sea, beneath the oceans, in places that people cannot even reach, the little creatures there eat a certain measured amount of things, and they never go hungry.

The Messenger of Allah (peace be upon him) says that if a person trusted Allah (swt) fully — not merely in words, but fully, from the heart, exactly as Allah (swt) has promised concerning rizq — that person would be like the birds. Birds leave their nests early in the morning with an empty stomach and come back to their nests with a full one. No bird has ever been heard complaining to its mate, or to its young, that there is no worm to be found that day; Allah (swt) provides for all of them. There is not a single moving, living creature on earth whose rizq He has not taken upon Himself to guarantee, and Allah (swt) definitely knows exactly where that particular creature — bird, or beast, or anything at all — stays at night, where its nest or its den lies, where it moves, and where it is going to die: all of it written in the Book of Allah, in al-Lawḥ al-Maḥfūẓ, the Preserved Tablet, completely, with not a single creature left out.