Surely Allah has bought of the believers their persons and their property for this, that they shall have the garden; they fight in Allah's way, so they slay and are slain; a promise which is binding on Him in the Taurat and the Injeel and the Quran; and who is more faithful to his covenant than Allah? Rejoice therefore in the pledge which you have made; and that is the mighty achievement.

And even if there were a Quran with which the mountains were made to pass away, or the earth were travelled over with it, or the dead were made to speak thereby; nay! the commandment is wholly Allah's, Have not yet those who believe known that if Allah please He would certainly guide all the people? And (as for) those who disbelieve, there will not cease to afflict them because of what they do a repelling calamity, or it will alight close by their abodes, until the promise of Allah comes about; surely Allah will not fail in (His) promise.

And thus have We sent it down an Arabic Quran, and have distinctly set forth therein of threats that they may guard (against evil) or that it may produce a reminder for them.

We know best what they say, and you are not one to compel them; therefore remind him by means of the Quran who fears My threat.