The word(s) "knowest" appears 15 time(s) in 14 verse(s) in Quran in Abdullah Yusuf Ali translation.

(11) Then were they confounded with shame: (they said), "Thou knowest full well that these (idols) do not speak!"

(12) knowest thou not that Allah knows all that is in heaven and on earth? Indeed it is all in a Record, and that is easy for Allah.

(13) "And thou didst a deed of thine which (thou knowest) thou didst, and thou art an ungrateful (wretch)!"

(14) O Prophet! When ye do divorce women, divorce them at their prescribed periods, and count (accurately), their prescribed periods: And fear Allah your Lord: and turn them not out of their houses, nor shall they (themselves) leave, except in case they are guilty of some open lewdness, those are limits set by Allah: and any who transgresses the limits of Allah, does verily wrong his (own) soul: thou knowest not if perchance Allah will bring about thereafter some new situation.