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

(21) Hast thou not turned Thy vision to those who have been given a portion of the Book? They are invited to the Book of Allah, to settle their dispute, but a party of them Turn back and decline (The arbitration).

(22) Say: "Obey Allah and His Messenger": But if they turn back, Allah loveth not those who reject Faith.

(23) But if they turn back, Allah hath full knowledge of those who do mischief.

(24) Say: "O People of the Book! come to common terms as between us and you: That we worship none but Allah; that we associate no partners with him; that we erect not, from among ourselves, Lords and patrons other than Allah." If then they turn back, say ye: "Bear witness that we (at least) are Muslims (bowing to Allah's Will).

(25) A section of the People of the Book say: "Believe in the morning what is revealed to the believers, but reject it at the end of the day; perchance they may (themselves) Turn back;

(26) Among the People of the Book are some who, if entrusted with a hoard of gold, will (readily) pay it back; others, who, if entrusted with a single silver coin, will not repay it unless thou constantly stoodest demanding, because, they say, "there is no call on us (to keep faith) with these ignorant (Pagans)." but they tell a lie against Allah, and (well) they know it.

(27) If any turn back after this, they are perverted transgressors.

(28) Do they seek for other than the Religion of Allah?-while all creatures in the heavens and on earth have, willing or unwilling, bowed to His Will (Accepted Islam), and to Him shall they all be brought back.

(29) To Allah belongs all that is in the heavens and on earth: To Him do all questions go back (for decision).

(30) They will do you no harm, barring a trifling annoyance; if they come out to fight you, they will show you their backs, and no help shall they get.