The word(s) "warn" appears 150 time(s) in 135 verse(s) in Quran in Mohsin Khan translation.

(31) And warn (O Muhammad صلى الله عليه و سلم) mankind of the Day when the torment will come unto them; then the wrong-doers will say: "Our Lord! Respite us for a little while, we will answer Your Call and follow the Messengers!" (It will be said): "Had you not sworn aforetime that you would not leave (the world for the Hereafter).

(32) This (Qur'an) is a Message for mankind (and a clear proof against them), in order that they may be warned thereby, and that they may know that He is the only One Ilah (God - Allah) - (none has the right to be worshipped but Allah) - and that men of understanding may take heed.

(33) And say (O Muhammad صلى الله عليه و سلم): "I am indeed a plain warner."

(34) He sends down the angels with the Ruh (revelation) of His Command to whom of His slaves He wills (saying): "warn mankind that La ilaha illa Ana (none has the right to be worshipped but I), so fear Me (by abstaining from sins and evil deeds).

(35) Whoever goes right, then he goes right only for the benefit of his ownself. And whoever goes astray, then he goes astray to his own loss. No one laden with burdens can bear another's burden. And We never punish until We have sent a Messenger (to give warning).

(36) And surely, We have explained [Our Promises, warnings and (set forth many) examples] in this Qur'an that they (the disbelievers) may take heed, but it increases them in naught save aversion.

(37) And nothing stops Us from sending the Ayat (proofs, evidence, signs) but that the people of old denied them. And We sent the she-camel to Thamud as a clear sign, but they did her wrong. And We sent not the signs except to warn, and to make them afraid (of destruction).

(38) And (remember) when We told you: "Verily! Your Lord has encompassed mankind (i.e. they are in His Grip)." And We made not the vision which we showed you (O Muhammad as an actual eye-witness and not as a dream on the night of Al-Isra' ) but a trial for mankind, and (likewise) the accursed tree (Zaqqum, mentioned) in the Qur'an. We warn and make them afraid but it only increases them in naught save great disbelief, oppression and disobedience to Allah.

(39) And with truth We have sent it down (i.e. the Qur'an), and with truth it has descended. And We have sent you (O Muhammad صلى الله عليه و سلم) as nothing but a bearer of glad tidings (of Paradise for those who follow your Message of Islamic Monotheism), and a warner (of Hell-fire for those who refuse to follow your Message of Islamic Monotheism) .

(40) (He has made it) straight to give warning (to the disbelievers) of a severe punishment from Him, and to give glad tidings to the believers (in the Oneness of Allah - Islamic Monotheism), who do righteous deeds, that they shall have a fair reward (i.e. Paradise).