The word(s) "back" appears 262 time(s) in 241 verse(s) in Quran in Muhammad Habib Shakir translation.

(21) Have you not considered those (Jews) who are given a portion of the Book? They are invited to the Book of Allah that it might decide between them, then a part of them turn back and they withdraw.

(22) Say: Obey Allah and the Apostle; but if they turn back, then surely Allah does not love the unbelievers.

(23) But if they turn back, then surely Allah knows the mischief-makers.

(24) Say: O followers of the Book! come to an equitable proposition between us and you that we shall not serve any but Allah and (that) we shall not associate aught with Him, and (that) some of us shall not take others for lords besides Allah; but if they turn back, then say: Bear witness that we are Muslims.

(25) And a party of the followers of the Book say: Avow belief in that which has been revealed to those who believe, in the first part of the day, and disbelieve at the end of it, perhaps they go back on their religion.

(26) And among the followers of the Book there are some such that if you entrust one (of them) with a heap of wealth, he shall pay it back to you; and among them there are some such that if you entrust one (of them) with a dinar he shall not pay it back to you except so long as you remain firm in demanding it; this is because they say: There is not upon us in the matter of the unlearned people any way (to reproach); and they tell a lie against Allah while they know.

(27) Whoever therefore turns back after this, these it is that are the transgressors.

(28) O you who believe! if you obey a party from among those who have been given the Book, they will turn you back as unbelievers after you have believed.

(29) They shall by no means harm you but with a slight evil; and if they fight with you they shall turn (their) backs to you, then shall they not be helped.

(30) And Muhammad is no more than an apostle; the apostles have already passed away before him; if then he dies or is killed will you turn back upon your heels? And whoever turns back upon his heels, he will by no means do harm to Allah in the least and Allah will reward the grateful.