Albert Barnes Commentary Jeremiah 49:1

"Of the children of Ammon. Thus saith Jehovah: Hath Israel no sons? hath he no heir? why then doth Malcam possess Gad, and his people well in the cities thereof?" — Jeremiah 49:1 (ASV)

Has Israel no sons? - that is, the Ammonites in seizing Gilead have acted as if the country had no rightful owner. The sons of Israel were to return from captivity, and the land was their hereditary property.

Their king - Milcom , see the margin. The Ammonite god stands for the Ammonites just as Chemosh (Jeremiah 48:7) is the equivalent of the Moabites.

Inherit - that is, take possession of.