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

(31) O you who believe! if you obey those who disbelieve they will turn you back upon your heels, so you will turn back losers.

(32) (As for) those of you who turned back on the day when the two armies met, only the Shaitan sought to cause them to make a slip on account of some deeds they had done, and certainly Allah has pardoned them; surely Allah is Forgiving, Forbearing.

(33) And it is not attributable to a prophet that he should act unfaithfully; and he who acts unfaithfully shall bring that in respect of which he has acted unfaithfully on the day of resurrection; then shall every soul be paid back fully what it has earned, and they shall not be dealt with unjustly.

(34) Those who said of their brethren whilst they (themselves) held back: Had they obeyed us, they would not have been killed. Say: Then avert death from yourselves if you speak the truth.

(35) And when Allah made a covenant with those who were given the Book: You shall certainly make it known to men and you shall not hide it; but they cast it behind their backs and took a small price for it; so evil is that which they buy.

(36) O you who have been given the Book! believe that which We have revealed, verifying what you have, before We alter faces then turn them on their backs, or curse them as We cursed the violaters of the Sabbath, and the command of Allah shall be executed.

(37) And surely among you is he who would certainly hang back! If then a misfortune befalls you he says: Surely Allah conferred a benefit on me that I was not present with them.

(38) Whoever obeys the Apostle, he indeed obeys Allah, and whoever turns back, so We have not sent you as a keeper over them.

(39) They desire that you should disbelieve as they have disbelieved, so that you might be (all) alike; therefore take not from among them friends until they fly (their homes) in Allah's way; but if they turn back, then seize them and kill them wherever you find them, and take not from among them a friend or a helper.

(40) You will find others who desire that they should be safe from you and secure from their own people; as often as they are sent back to the mischief they get thrown into it headlong; therefore if they do not withdraw from you, and (do not) offer you peace and restrain their hands, then seize them and kill them wherever you find them; and against these We have given you a clear authority.