The Commander of the Faithful, Ali (peace be upon him), was asked: What is the source of the stability of faith? He said: “Piety.” He was asked: What is its decline? He said: “Greed.”

 Al-Aسُئِلَ أميرُ المُؤمِنينَ عَلِيُّ بنُ أبي طالِبٍ عليه السلام : ما ثَباتُ الإِيمانِ ؟ فَقالَ : الوَرَعُ ، فَقيلَ لَهُ : ما زَوالُهُ ؟ قالَ : الطَّمَعُ .mali for Saduq: p. 365, h. 454

The Supreme Leader’s :

We have repeatedly heard from the great people of meaning and monotheism that the first recommendation is to abandon sin, then comes the turn to do good deeds, remembrance, adhkar, nawafil, mustahabb, and the like. The first is to abandon sin.