The word(s) "behind" appears 57 time(s) in 56 verse(s) in Quran in Muhammad Habib Shakir translation.

(51) Those who are left behind will say when you set forth for the gaining of acquisitions: Allow us (that) we may follow you. They desire to change the world of Allah. Say: By no means shall you follow us; thus did Allah say before. But they will say: Nay! you are jealous of us. Nay! they do not understand but a little.

(52) Say to those of the dwellers of the desert who were left behind: You shall soon be invited (to fight) against a people possessing mighty prowess; you will fight against them until they submit; then if you obey, Allah will grant you a good reward; and if you turn back as you turned back before, He will punish you with a painful punishment.

(53) (As for) those who call out to you from behind the private chambers, surely most of them do not understand.

(54) They will not fight against you in a body save in fortified towns or from behind walls; their fighting between them is severe, you may think them as one body, and their hearts are disunited; that is because they are a people who have no sense.

(55) To him among you who wishes to go forward or remain behind.

(56) And as to him who is given his book behind his back,