The book of Leviticus as well as the book of Numbers follow immediately after the book of Exodus. The book of Numbers begins with the words "And the Lord spake unto Moses in the wilderness of Sinaï, in the tabernacle of the congregation, on the first day of the second month, in the second year after they were come out of the land of Egypt" (c.f. Exod 40:17)
The Lord Jesus includes the book of Numbers in His words when explaining to His disciples all that was written concerning Himself ("in the law of Moses, and in the prophets, and in the psalms" Lk 24:44).
Dale Ralph Davis, Numbers with Dale Ralph Davis.