The word(s) "fruitless" appears 6 time(s) in 6 verse(s) in Quran in Mohsin Khan translation.

(1) Made lawful to you this day are At-Tayyibat [all kinds of Halal (lawful) foods, which Allah has made lawful (meat of slaughtered eatable animals, milk products, fats, vegetables and fruits)]. The food (slaughtered cattle, eatable animals) of the people of the Scripture (Jews and Christians) is lawful to you and yours is lawful to them. (Lawful to you in marriage) are chaste women from the believers and chaste women from those who were given the Scripture (Jews and Christians) before your time when you have given their due Mahr (bridal-money given by the husband to his wife at the time of marriage), desiring chastity (i.e. taking them in legal wedlock) not committing illegal sexual intercourse, nor taking them as girl-friends. And whosoever disbelieves in Faith [i.e. in the Oneness of Allah and in all the other Articles of Faith i.e. His (Allah's) Angels, His Holy Books, His Messengers, the Day of Resurrection and Al-Qadar (Divine Preordainments)], then fruitless is his work; and in the Hereafter he will be among the losers.

(2) Being miserly towards you (as regards help and aid in Allah's Cause). Then when fear comes, you will see them looking to you, their eyes revolving like (those of) one over whom hovers death; but when the fear departs, they will smite you with sharp tongues, miserly towards (spending anything in any) good (and only covetous of booty and wealth). Such have not believed. Therefore Allah makes their deeds fruitless and that is ever easy for Allah.

(3) That is because they hate that which Allah has sent down (this Qur'an and Islamic laws, etc.); so He has made their deeds fruitless.

(4) That is because they followed that which angered Allah and hated that which pleased Him. So He made their deeds fruitless.

(5) Verily, those who disbelieve, and hinder (men) from the Path of Allah (i.e. Islam), and oppose the Messenger (صلى الله عليه وسلم) (by standing against him and hurting him), after the guidance has been clearly shown to them, they will not harm Allah in the least, but He will make their deeds fruitless,

(6) O you who believe! Raise not your voices above the voice of the Prophet (صلى الله عليه وسلم), nor speak aloud to him in talk as you speak aloud to one another, lest your deeds should be rendered fruitless while you perceive not.