I heard the Messenger of Allah ﷺ say, "Ali is from me and I am from him, and none shall fulfill my obligations on my behalf except Ali."
حدثنا أبو بكر بن أبي شيبة وسويد بن سعيد وإسمعيل بن موسى قالوا حدثنا شريك عن أبي إسحق
سمعت رسول الله ﷺ يقول علي مني وأنا منه ولا يؤدي عني إلا علي
Sourcing, hasan. Tirmidhi narrated it in Manaqib, chapter "Ali is from me and I am from Ali," no. 3719, from Ismail with this chain, and he said, hasan gharib sahih. Sharik was corroborated by Israil and others, and Abu Ishaq explicitly stated that he heard it directly.