The word(s) "believing" appears 32 time(s) in 24 verse(s) in Quran in Abdullah Yusuf Ali translation.

(21) Hast thou not observed the Hypocrites say to their misbelieving brethren among the People of the Book? - "If ye are expelled, we too will go out with you, and we will never hearken to any one in your affair; and if ye are attacked (in fight) we will help you". But Allah is witness that they are indeed liars.

(22) O ye who believe! When there come to you believing women refugees, examine (and test) them: Allah knows best as to their Faith: if ye ascertain that they are Believers, then send them not back to the Unbelievers. They are not lawful (wives) for the Unbelievers, nor are the (Unbelievers) lawful (husbands) for them. But pay the Unbelievers what they have spent (on their dower), and there will be no blame on you if ye marry them on payment of their dower to them. But hold not to the guardianship of unbelieving women: ask for what ye have spent on their dowers, and let the (Unbelievers) ask for what they have spent (on the dowers of women who come over to you). Such is the command of Allah: He judges (with justice) between you. And Allah is Full of Knowledge and Wisdom.

(23) O Prophet! When believing women come to thee to take the oath of fealty to thee, that they will not associate in worship any other thing whatever with Allah, that they will not steal, that they will not commit adultery (or fornication), that they will not kill their children, that they will not utter slander, intentionally forging falsehood, and that they will not disobey thee in any just matter,- then do thou receive their fealty, and pray to Allah for the forgiveness (of their sins): for Allah is Oft-Forgiving, Most Merciful.

(24) "O my Lord! Forgive me, my parents, all who enter my house in Faith, and (all) believing men and believing women: and to the wrong-doers grant Thou no increase but in perdition!"