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

(1) But for the Grace of Allah to thee and his Mercy, a party of them would certainly have plotted to lead thee astray. But (in fact) they will only Lead their own souls astray, and to thee they can do no harm in the least. For Allah hath sent down to thee the Book and wisdom and taught thee what thou knewest not (before): And great is the Grace of Allah unto thee.

(2) And thus have We, by Our Command, sent inspiration to thee: thou knewest not (before) what was Revelation, and what was Faith; but We have made the (Qur'an) a Light, wherewith We guide such of Our servants as We will; and verily thou dost guide (men) to the Straight Way,-