Amos 1:9

"Thus saith Jehovah: For three transgressions of Tyre, yea, for four, I will not turn away the punishment thereof; because they delivered up the whole country to Edom, and remembered not the brotherly covenant.

The great sin of Tyre mentioned here is their delivery of Hebrew slaves to their bitterest enemies, the Edomites, and that this was done despite the long record of friendship between Israel and Tyre, dating back to the days of Solomon, and the brotherly covenant of mutual respect and honor which existed between the two peoples. "No king of Israel or Judah had ever made war on Phoenicia."[34] The indifference and cruelty of Phoenicia, the great slave traders of the day, in their dealings with the covenant people of God, ultimately issued in God's destructive judgment against them. The friendliness between Tyre and Israel is mentioned in the O.T. (2 Samuel 5:11; 1 Kings 5:1; 9:11,14, etc.); and, although there is no mention of any formal treaty existing between them, the relationship, "doubtless had occasionally been cemented by formal treaty."[35] At any rate, there was a "covenant," as indicated by this verse. The Tyrians had considered themselves bound by no consideration of human rights and free to violate any honor for the sake of their profitable slave trade.