Al-Matalib al-'Aliyah 2936 — The fundamentals of the religion

It is narrated from Sayyiduna Ali bin Abi Talib (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) said: "Three things are among the root and foundation of the religion: (first) that you pray the Friday prayer behind every righteous and sinful (imam or ruler); (second) that the funeral prayer be offered for whoever dies from the people of the qiblah; and (third) that jihad be continued under the leadership of whoever the caliph may be. You will certainly receive your reward for this."
[Takhrij: This narration is in Musnad Ishaq bin Rahwayh: 474; its chain contains a narrator named Muhammad bin Ulwan, who is majhul (unknown), though the matters mentioned in the hadith are established by the agreed beliefs of Ahl al-Sunnah and by other authentic hadith].