Musnad Abu Ya'la al-Mawsili 109:324

Abu Sa’id al-Qawariri narrated to us, Muhammad ibn ‘Uthman al-Qurashi narrated to us, Sulayman narrated to us, from Abu al-Zubayr, from Jabir, from the Prophet (peace and blessings of Allah be upon him): "If the *musinnah* (full-grown animal) of sheep becomes difficult for you, then the *jadha’* (six-month-old lamb) of sheep is sufficient."