The word(s) "necessary" appears 3 time(s) in 2 verse(s) in Quran in Abdullah Yusuf Ali translation.

(1) O people of the Book! There hath come to you our Messenger, revealing to you much that ye used to hide in the Book, and passing over much (that is now unnecessary): There hath come to you from Allah a (new) light and a perspicuous Book, -

(2) Behold! Thou didst say to one who had received the grace of Allah and thy favour: "Retain thou (in wedlock) thy wife, and fear Allah." But thou didst hide in thy heart that which Allah was about to make manifest: thou didst fear the people, but it is more fitting that thou shouldst fear Allah. Then when Zaid had dissolved (his marriage) with her, with the necessary (formality), We joined her in marriage to thee: in order that (in future) there may be no difficulty to the Believers in (the matter of) marriage with the wives of their adopted sons, when the latter have dissolved with the necessary (formality) (their marriage) with them. And Allah's command must be fulfilled.