Sayyiduna Jabir bin Abdullah (may Allah be pleased with him) reports that the Messenger of Allah (peace and blessings be upon him) said: Whoever among you thinks that he will not be able to wake up in the last part of the night, then he should perform Witr at the beginning of the night. But whoever thinks that he will wake up in the last part of the night, then he should perform Witr at its end, because the prayer in the last part of the night is attended by the angels and it is the best.