Amos 6:8

The prophet announced further that sovereign Yahweh of hosts, even He, had sworn by Himself (cf. Amos 4:2; Amos 8:7). This was a solemn warning because God can swear by no one greater than Himself (cf. Hebrews 6:13-14). He loathed the pride of Jacob. "Jacob" here refers to the Northern Kingdom (cf. Amos 3:13), and "the pride of Jacob" is probably the city of Samaria. [Note: See Hayes, p. 188.] In their self-confidence, these leaders resembled their forefather Jacob. The Lord also hated their fortified mansions from which they oppressed the poor and needy (cf. Amos 3:9-10).

"The mighty fortress is their god. Its security and power make God’s protection and blessing irrelevant crutches in the real world of economic and political influence." [Note: G. Smith, Amos: A Commentary, p. 207.]

Therefore Yahweh would fight against them and deliver up Samaria and all it contained to an enemy.