سورة الزمر

Ali ibn Ibrahim (may Allah have mercy on him): أَلَیْسَ اللهُ بِکَافٍ عَبْدَهُ وَ یُخَوِّفُونَکَ بِالَّذِینَ مِن دُونِهِ [Is not Allah sufficient for His servant? And they seek to frighten you with those besides Him] — that is, [the hypocrites] say to you: "O Muhammad (peace be upon him and his family)! Excuse us from accepting the matter of the wilayah (guardianship) of Ali (peace be upon him)," and they frighten you that, if you insist on their accepting the wilayah of Ali (peace be upon him), they may join the disbelievers and abandon Islam.

Imam Sadiq (peace be upon him): By Allah! If the inhabitants of the heavens and the earths were to gather together to guide a servant whom Allah has willed to lead astray, they would not be able to guide him; and if the inhabitants of the heavens and the earths were to gather together to lead astray a servant whom Allah has willed to guide, they would not be able to lead him astray. Withhold yourselves from people, and let no one say, "This is my brother," or "my cousin," or "my neighbour." Whenever Allah wills to bring good to a servant, He purifies his soul, so that he does not hear any good deed without recognising it, nor any wrong without rejecting it; then Allah casts into his heart a word by which all his affairs are ordered.