The word(s) "back" appears 225 time(s) in 216 verse(s) in Quran in Abdullah Yusuf Ali translation.

(61) On the Day when heat will be produced out of that (wealth) in the fire of Hell, and with it will be branded their foreheads, their flanks, and their backs, their flanks, and their backs.- "This is the (treasure) which ye buried for yourselves: taste ye, then, the (treasures) ye buried!"

(62) They swear by Allah that they said nothing (evil), but indeed they uttered blasphemy, and they did it after accepting Islam; and they meditated a plot which they were unable to carry out: this revenge of theirs was (their) only return for the bounty with which Allah and His Messenger had enriched them! If they repent, it will be best for them; but if they turn back (to their evil ways), Allah will punish them with a grievous penalty in this life and in the Hereafter: They shall have none on earth to protect or help them.

(63) But when He did bestow of His bounty, they became covetous, and turned back (from their covenant), averse (from its fulfilment).

(64) Those who slander such of the believers as give themselves freely to (deeds of) charity, as well as such as can find nothing to give except the fruits of their labour,- and throw ridicule on them,- Allah will throw back their ridicule on them: and they shall have a grievous penalty.

(65) Those who were left behind (in the Tabuk expedition) rejoiced in their inaction behind the back of the Messenger of Allah: they hated to strive and fight, with their goods and their persons, in the cause of Allah: they said, "Go not forth in the heat." Say, "The fire of Hell is fiercer in heat." If only they could understand!

(66) If, then, Allah bring thee back to any of them, and they ask thy permission to come out (with thee), say: "Never shall ye come out with me, nor fight an enemy with me: for ye preferred to sit inactive on the first occasion: Then sit ye (now) with those who lag behind."

(67) Nor (is there blame) on those who came to thee to be provided with mounts, and when thou saidst, "I can find no mounts for you," they turned back, their eyes streaming with tears of grief that they had no resources wherewith to provide the expenses.

(68) They will present their excuses to you when ye return to them. Say thou: "Present no excuses: we shall not believe you: Allah hath already informed us of the true state of matters concerning you: It is your actions that Allah and His Messenger will observe: in the end will ye be brought back to Him Who knoweth what is hidden and what is open: then will He show you the truth of all that ye did."

(69) And say: "Work (righteousness): Soon will Allah observe your work, and His Messenger, and the Believers: Soon will ye be brought back to the knower of what is hidden and what is open: then will He show you the truth of all that ye did."

(70) There will every soul prove (the fruits of) the deeds it sent before: they will be brought back to Allah their rightful Lord, and their invented falsehoods will leave them in the lurch.