The word(s) "lest" appears 73 time(s) in 69 verse(s) in Quran in Abdullah Yusuf Ali translation.

(11) lest ye should say: "The Book was sent down to two Peoples before us, and for our part, we remained unacquainted with all that they learned by assiduous study:"

(12) Or lest ye should say: "If the Book had only been sent down to us, we should have followed its guidance better than they." Now then hath come unto you a clear (sign) from your Lord,- and a guide and a mercy: then who could do more wrong than one who rejecteth Allah's signs, and turneth away therefrom? In good time shall We requite those who turn away from Our signs, with a dreadful penalty, for their turning away.

(13) Then began Satan to whisper suggestions to them, bringing openly before their minds all their shame that was hidden from them (before): he said: "Your Lord only forbade you this tree, lest ye should become angels or such beings as live for ever."

(14) They said: "Comest thou to us, that we may worship Allah alone, and give up the cult of our fathers? bring us what thou threatenest us with, if so be that thou tellest the truth!"

(15) (Pharaoh) said: "If indeed thou hast come with a Sign, show it forth,- if thou tellest the truth."

(16) When thy Lord drew forth from the Children of Adam - from their loins - their descendants, and made them testify concerning themselves, (saying): "Am I not your Lord (who cherishes and sustains you)?"- They said: "Yea! We do testify!" (This), lest ye should say on the Day of Judgment: "Of this we were never mindful":

(17) Or lest ye should say: "Our fathers before us may have taken false gods, but we are (their) descendants after them: wilt Thou then destroy us because of the deeds of men who were futile?"

(18) If thou callest them to guidance, they hear not. Thou wilt see them looking at thee, but they see not.

(19) And obey Allah and His Messenger; and fall into no disputes, lest ye lose heart and your power depart; and be patient and persevering: For Allah is with those who patiently persevere:

(20) Among them are men who molest the Prophet and say, "He is (all) ear." Say, "He listens to what is best for you: he believes in Allah, has faith in the Believers, and is a Mercy to those of you who believe." But those who molest the Messenger will have a grievous penalty.