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

(1) And (remember) when We took a covenant from the Children of Israel, (saying): Worship none but Allah (Alone) and be dutiful and good to parents, and to kindred, and to orphans and Al-Masakin (the poor), and speak good to people [i.e. enjoin righteousness and forbid evil, and say the truth about Muhammad صلى الله عليه وسلم], and perform As-Salat (Iqamat-as-Salat), and give Zakat. Then you slid back, except a few of you, while you are backsliders. (Tafsir Al-Qurtubi).

(2) And when there came to them a Messenger from Allah (i.e. Muhammad صلى الله عليه وسلم) confirming what was with them, a party of those who were given the Scripture threw away the Book of Allah behind their backs as if they did not know!

(3) They ask you (O Muhammad صلى الله عليه وسلم) about the new moons. Say: These are signs to mark fixed periods of time for mankind and for the pilgrimage. It is not Al-Birr (piety, righteousness) that you enter the houses from the back but Al-Birr (is the quality of the one) who fears Allah. So enter houses through their proper doors, and fear Allah that you may be successful.

(4) Then if you slide back after the clear signs (Prophet Muhammad صلى الله عليه وسلم and this Qur'an, and Islam) have come to you, then know that Allah is All-Mighty, All-Wise.

(5) They ask you concerning fighting in the Sacred Months (i.e. 1st, 7th, 11th and 12th months of the Islamic calendar). Say "Fighting therein is a great (transgression) but a greater (transgression) with Allah is to prevent mankind from following the Way of Allah, to disbelieve in Him, to prevent access to Al-Masjid-Al-Haram (at Makkah), and to drive out its inhabitants, and Al-Fitnah is worse than killing. And they will never cease fighting you until they turn you back from your religion (Islamic Monotheism) if they can. And whosoever of you turns back from his religion and dies as a disbeliever, then his deeds will be lost in this life and in the Hereafter, and they will be the dwellers of the Fire. They will abide therein forever."

(6) And divorced women shall wait (as regards their marriage) for three menstrual periods, and it is not lawful for them to conceal what Allah has created in their wombs, if they believe in Allah and the Last Day. And their husbands have the better right to take them back in that period, if they wish for reconciliation. And they (women) have rights (over their husbands as regards living expenses) similar (to those of their husbands) over them (as regards obedience and respect) to what is reasonable, but men have a degree (of responsibility) over them. And Allah is All-Mighty, All-Wise.

(7) The divorce is twice, after that, either you retain her on reasonable terms or release her with kindness. And it is not lawful for you (men) to take back (from your wives) any of your Mahr (bridal-money given by the husband to his wife at the time of marriage) which you have given them, except when both parties fear that they would be unable to keep the limits ordained by Allah (e.g. to deal with each other on a fair basis). Then if you fear that they would not be able to keep the limits ordained by Allah, then there is no sin on either of them if she gives back (the Mahr or a part of it) for her Al-Khul' (divorce) . These are the limits ordained by Allah, so do not transgress them. And whoever transgresses the limits ordained by Allah, then such are the Zalimun (wrong-doers).

(8) And when you have divorced women and they have fulfilled the term of their prescribed period, either take them back on reasonable basis or set them free on reasonable basis. But do not take them back to hurt them, and whoever does that, then he has wronged himself. And treat not the Verses (Laws) of Allah as a jest, but remember Allah's Favours on you (i.e. Islam), and that which He has sent down to you of the Book (i.e. the Qur'an) and Al-Hikmah (the Prophet's Sunnah - legal ways - Islamic jurisprudence.) whereby He instructs you. And fear Allah, and know that Allah is All-Aware of everything.

(9) And be afraid of the Day when you shall be brought back to Allah. Then every person shall be paid what he earned, and they shall not be dealt with unjustly.

(10) And a party of the people of the Scripture say: "Believe in the morning in that which is revealed to the believers (Muslims), and reject it at the end of the day, so that they may turn back.