Musnad Ahmad

It is narrated from Asim bin Ubaidullah that the Prophet (peace and blessings be upon him) said: After me, there will come some rulers who will sometimes perform the prayer at its appointed time and sometimes delay it. You should continue to pray with them; if they pray at the proper time and you join them, you will receive the reward and so will they. If they delay it and you still pray with them, you will receive the reward and they will bear the punishment for the delay. Whoever separates himself from the congregation and dies in that state, dies the death of ignorance (Jahiliyyah). And whoever breaks a covenant and dies in that state, will come on the Day of Resurrection with no argument in his favor. Ibn Jurayj says: I asked Asim, "Who narrated this hadith to you?" He replied, "Abdullah bin Amir narrated it to me from his father, and he from the Prophet (peace and blessings be upon him)."