Amasa was David's nephew, the son of Abigail, who was David's sister. He was also a cousin to Joab, the commander of David's army. Absalom appointed Amasa as commander of his army, when he rebelled against David. After David's army defeated the rebel forces, and Joab had killed Absalom, David forgave Amasa and appointed him commander of his army. In return for this kindness, Amasa convinced all the leaders of Judah to take back David as their king after the revolt of Absalom.
When David sent Amasa to mobilize the troops to chase after Sheba, he met up with Joab and Abishai, who were leading the king's bodyguard on the same mission. Amasa and Joab went to greet each other, but Joab pulled out a dagger and killed Amasa.
The name Amasa (Hebrew: עֲמָשָׂא ) means "burden". As the son of an Ishmaelite proselyte named Jether (Israelite name Ithra, a variant) and Jesse's step daughter Abigail, Moabitess, this may have been a commentary on the regime of King Saul, who was harsh on his neighbors.
Background and family
Amasa was born to a Jether, an Ishmaelite who apparently lived among the Moabites across the Jordan River from Bethlehem in Judah. His mother was a woman named Abigail, the daughter of Nahash, of Moabite nobility. Sometime before David was born, his father had married Abigail's mother, making her David's step sister. She would have a half-sister named Zeruiah, Joab's mother.
As a child living in the town with Jesse, Amasa would have been quite aware of the manic Benjamite the people had selected for their king. Though a nephew of David, he nearer to the age of his uncles than to own cousins. It is certain he would have been intrigued as Samuel came around to anoint young David. Having grown up an adopted Israelite, he knew that Yahweh worked among the people, in spite of the chaos.