Allah Taala said in the Quran:
Say: I am only a mortal like you; it is revealed to me that your god is one Allah, therefore whoever hopes to meet his Lord, he should do good deeds, and not join any one in the service of his Lord.
Let us see shia commentary of this verse.
Al-Ayashi in his commentary (2/353) said:
عن سماعة بن مهران قال: سألت ابا عبد الله عليه السلام عن قول الله: (فليعمل عملا صالحا ولا يشرك بعبادة ربه احدا) قال: العمل الصالح المعرفة بالائمة، (ولا يشرك بعبادة ربه احدا) التسليم لعلى لا يشرك معه في الخلافة من ليس ذلك له ولا هو من أهله
From Sulaiman ibn Mihran: “I asked Abu Abdullah (alaihi salam) about saying of Allah “he should do good deeds, and not join any one in the service of his Lord”. He said: “Good deeds” that’s knowledge of imams, and “not join any one in the service of his Lord” mean submit yourself to Ali, and don’t make partners with him in the caliphate from those who has no share in that, and who is not from its people.