The word(s) "back" appears 161 time(s) in 150 verse(s) in Quran in Mohsin Khan translation.

(101) So verily, you (O Muhammad صلى الله عليه وسلم) cannot make the dead to hear (i.e. the disbelievers), nor can you make the deaf to hear the call, when they show their backs and turn away.

(102) And if you only could see when the Mujrimun (criminals, disbelievers, polytheists, sinners) shall hang their heads before their Lord (saying): "Our Lord! We have now seen and heard, so send us back (to the world), that we will do righteous good deeds. Verily! We now believe with certainty."

(103) And as for those who are Fasiqun (disbelievers and disobedient to Allah), their abode will be the Fire, every time they wish to get away therefrom, they will be put back thereto, and it will be said to them: "Taste you the torment of the Fire which you used to deny."

(104) Allah has not made for any man two hearts inside his body. Neither has He made your wives whom you declare to be like your mothers' backs, your real mothers. [az-Zihar is the saying of a husband to his wife, "You are to me like the back of my mother" i.e. You are unlawful for me to approach], nor has He made your adopted sons your real sons. That is but your saying with your mouths. But Allah says the truth, and He guides to the (Right) Way.

(105) And when a party of them said: "O people of Yathrib (Al-Madinah)! There is no stand (possible) for you (against the enemy attack!) Therefore go back!" And a band of them ask for permission of the Prophet (صلى الله عليه وسلم) saying: "Truly, our homes lie open (to the enemy)." And they lay not open. They but wished to flee.

(106) And indeed they had already made a covenant with Allah not to turn their backs, and a covenant with Allah must be answered for.

(107) Allah already knows those among you who keep back (men) from fighting in Allah's Cause, and those who say to their brethren "Come here towards us," while they (themselves) come not to the battle except a little,

(108) Among the believers are men who have been true to their covenant with Allah [i.e. they have gone out for Jihad (holy fighting), and showed not their backs to the disbelievers]; of them some have fulfilled their obligations (i.e. have been martyred); and some of them are still waiting, but they have never changed [i.e. they never proved treacherous to their covenant which they concluded with Allah] in the least.

(109) And Allah drove back those who disbelieved in their rage: they gained no advantage (booty). Allah sufficed for the believers in the fighting (by sending against the disbelievers a severe wind and troops of angels). And Allah is Ever All-Strong, All-Mighty.

(110) And those of the people of the Scripture who backed them (the disbelievers), Allah brought them down from their forts and cast terror into their hearts, (so that) a group (of them) you killed, and a group (of them) you made captives.