Please don't beat me up saleel, a bro asked me this, and I couldn't answer.
Allah's mercy overcomes his wrath, right? As long as we testify and, with conviction, believe, that there is no god but Allah and Muhammad is his messenger, eternal punishment in hell is forbidden for us, right? A few million years in hell is minor because eternity in heaven will eradicate any feeling of distress from hell and the pleasure will override any pain.
He's not saying that something is impermissible for Allah but rather Allah has promised jannah for those who believe. So then, why should we strive to avoid sin, when afterall, we'll only burn in hellfire for a limited amount of time thereafter go to jannah for eternity - automatically wiping out any trace of hellfire???