The Messenger of Allah ﷺ said, "Do not sacrifice anything but a fully grown animal, unless it is difficult for you, in which case you may slaughter a young sheep."
قال رسول الله ﷺ: لا تذبحوا إلا مسنة، إلا أن يعسر عليكم فتذبحوا جذعة من الضأن.
Muslim narrated it in the Book of Sacrifices (1963), from Ahmad bin Yunus, who said, Zuhayr told us, Abu Zubayr told us, from Jabir, and he mentioned it.Nawawi said, "This is an explicit statement that a jaza (a young animal under the required age) is not permissible except from sheep, under any circumstance. This is a matter of consensus, as reported by Qadi Iyad. Abdari and others among our fellow scholars reported from Uzai that he said, 'A jaza suffices from camels, cattle, goats, and sheep alike,' and this same view was also reported from Ataa." Sharh Sahih Muslim (13/117).As for his saying, "except a musinnah," the musinnah is the thaniyyah (an animal that has shed its milk teeth) of any kind, whether camel, cattle, or sheep.