It is narrated from Sayyiduna Abu Ayyub (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "Witr is five, or three, or one rak'ah; and if you are not able, then pray it by gestures." (This is the wording of the narration of Sa'id bin Sulayman.)
Hadith Referenceالمعجم الكبير للطبراني / باب الخاء / 3948