Hadith

 وبهذا الاسناد، عن الحسن بن عليّ، عن عاصم بن حميد، عن أبي إسحاق النحوي قال: سمعت أبا عبد الله عليه السلام يقول: إنّ الله أدّب نبيّه صلّى الله عليه وآله على محبّته فقال: (وَإِنَّكَ لَعَلَى خُلُق عَظِيم). ثمّ فوّض إليه فقال: (وَمَا آتَاكُمُ الرَّسُولُ فَخُذُوهُ وَمَا نَهَاكُمْ عَنْهُ فَانْتَهُوا). وقال: (مَنْ يُطِعِ الرَّسُولَ فَقَدْ أَطَاعَ اللهَ.) وإنّ رسول الله صلّى الله عليه وآله فوّض إلى عليّ عليه السلام فائتمنه فسلّمتم وجحد الناس. فوالله لنحبّكم أن تقولوا إذا قلنا، وتصمتوا إذا صمتنا، ونحن فيما بينكم وبين الله، والله ما جعل لأحد من خير في خلاف أمره.

 (The same previous series of relaters) …from al-Hasan bin Ali from Aassim bin Hamid that Abu Ishaq an-Nahawi (the grammarian) said that he heard Abu Abdullah (a) saying: Allah educated His Prophet (s) as He liked for him. He says: "You have attained a high moral standard (68:4)." Allah then authorized him to represent Him. He says: "Take only what the Messenger gives to you and desist from what he forbids you (59:7)." "One who obeys the Messenger has certainly obeyed Allah (4:80)." In the same manner, the Prophet (s) authorized Ali (a) to represent him and deposited with him (all the religious affairs). You submitted (to this authority) while the others denied. By Allah I swear, we do love you to say when we say and keep silent when we keep silent. We are the mediators between Allah and you. Allah has never made any goodness lie in the contradiction to His commandments.

Faḍaʾil al-Shīʿa

Book 1, Chapter 30