And Allah, exalted be He, has spoken about reliance upon Him: “Place your trust in Allah if you are truly believers” (5:23) and, “So let those who trust, put their trust in Allah” (14:12). He also says: “Say, ‘Allah is sufficient for me; in Him do those who trust place their trust’” (39:38). And He says: “If only they had been content with what Allah and His Messenger gave them and had said, ‘Allah is sufficient for us; Allah will surely grant us of His bounty, and so will His Messenger. To Allah alone do we turn with longing’” (9:59).
Notice that, when speaking of giving, He said, “what Allah and His Messenger gave them,” whereas when speaking of reliance He said, “Allah is sufficient for us,” and did not add, “and His Messenger.” The reason is that bestowal here refers to a legislative grant that includes permission and lawful dispensation conveyed by the Messenger— for what he pronounces lawful is lawful, what he pronounces unlawful is unlawful, and the religion is whatever he has prescribed. The Almighty states: “Whatever the Messenger gives you, take it, and whatever he forbids you, abstain from it” (59:7).
As for ḥasab (the one who suffices), it means the One who is enough, and Allah alone suffices for His servant, as He says: “Those to whom the people said, ‘Indeed, the people have gathered against you, so fear them…’”