Sayyiduna Abu Umamah (may Allah be pleased with him) narrated that when the time of the Battle of Khaybar came, the Messenger of Allah (peace and blessings be upon him) said: "We will fall upon them in the morning, so lighten (your provisions) and gather your strength."
Hadith Referenceالمعجم الكبير للطبراني / باب الصاد / 7903