Musnad Ahmad 28:492

'Abd al-Samad narrated to us, Khalifah narrated to us, from 'Amr ibn Shu'ayb, from his father, from his grandfather, that the Messenger of Allah (peace and blessings of Allah be upon him) addressed them while his back was leaning against the Ka'bah, and he said: "There is no prayer after the 'Asr (afternoon) prayer until the sun sets, and there is no prayer after the Ghadah (dawn) prayer until the sun rises. The blood of the believers is equal; the lowest of them strives for their protection, and they are a united hand against those who are other than them. Beware, a believer shall not be killed for a disbeliever, nor shall one who has a covenant be killed while in his covenant."