In the Book of Genesis, Shem is named first in the account of Noah’s family leaving the Ark. Genesis 8:18 says Noah went out with his sons, and Genesis 9:18 identifies the sons as Shem, Ham, and Japheth in that order.
The three sons are introduced earlier in Genesis 5:32 and 6:10. They accompany Noah and their wives through the Flood and become the ancestors of peoples in the post-Flood genealogical narrative. Genesis 9 later focuses on an incident involving Noah, Ham, and Ham’s son Canaan.
The order of names can be easy to overlook because another passage, Genesis 10:21, describes Japheth as the elder brother of Shem in many translations or interpretations. Biblical name order does not always function as a simple statement of birth order.
Shem is also the ancestor associated with the line leading to Abraham in the genealogy of Genesis 11. That later genealogy helps explain why his name receives sustained attention.