But Allah would not punish them while you, [O Muhammad], are among them, and Allah would not punish them while they seek forgiveness.
[Qur'aan 8:33]
Indeed, the devil said: I swear by Your Izzah O Lord, I will not stop misguiding Your slaves as long as their 'arwaah are in their bodies. Thereupon, the Lord said: I swear by My Izzah and by My Jalaal, I will not stop forgiving them as long as they keep asking Me forgiveness.
Shiekh al-albaani says the hadith reaches the grade of Hasan when all its routes of transmission are taken into consideration.
It has been attributed to Ibn Abbaas that he said that there are two forms of security in this Ummah. One has been taken [i.e. the Messenger of Allaah (sallallaahu alayhi wa sallam)]. The other, seeking forgiveness, remains.