narrated sahl bin sad (radi-allahu 'anhu):

a lady came to the prophet (sallallahu 'alaihi wa sallam) and declared that she had decided to offer herself to allah and his apostle (sallallahu 'alaihi wa sallam). the prophet (sallallahu 'alaihi wa sallam) said, "i am not in need of women." a man said to the prophet (sallallahu 'alaihi wa
sallam), "please marry her to me." the prophet (sallallahu 'alaihi wa sallam) said (to him), "give her a garment." the man said, "i cannot afford
it." the prophet (sallallahu 'alaihi wa sallam) said, "give her anything, even if it were an iron ring." the man apologised again. the prophet (sallallahu 'alaihi wa sallam) then asked him, "what do you know by heart of the qur'an?" he replied, "i know such-and-such portion of the qur'an (by heart)." the prophet (sallallahu 'alaihi wa sallam) said, "then i marry her to you for that much of the qur'an which you know by heart."

bukhari vol. 6 : no. 547