Sayyiduna Uqbah bin Amr (may Allah be pleased with him) and Sayyiduna Abu Musa al-Ash'ari (may Allah be pleased with him) narrate: The Prophet (peace and blessings be upon him) would sometimes perform the witr in the early part of the night or in its middle part, so that there would be latitude for the Muslims.
Imam al-Tabarani recorded this narration in al-Mu'jam al-Kabir; the chain of this narration contains a person who is da'if al-hadith (weak in hadith).