Silsilah as-Sahihah 820 — When to pray Witr

Sayyiduna Jabir (may Allah be pleased with him) narrates that the Messenger of Allah (peace and blessings be upon him) said: "Whoever fears that he may not be able to wake up in the last part of the night should perform the Witr prayer at the beginning of the night. And whoever hopes to wake up in the last part of the night should perform Witr in the last part of the night, for the prayer in the last part of the night is attended by angels and it is superior."