2 Kings 3:27

Overview - 2 Kings 3
Jehoram's reign.
Mesha rebels.
Jehoram, with Jehoshaphat, and the king of Edom, being distressed for want of water, by Elisha obtains water, and promise of victory.
21 The Moabites, deceived by the colour of the water, coming to spoil, are overcome.
26 The king of Moab, failing in his attempt to break through to the king of Edom, sacrifices his son, and raises the siege.
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2 Kings 3:27  (King James Version)
Then he took his eldest son that should have reigned in his stead, and offered him for a burnt offering upon the wall. And there was great indignation against Israel: and they departed from him, and returned to their own land.

offered him
In cases of great extremity, it was customary in various heathen nations, to offer human sacrifices, and even their own children. This was frequent among the Phoenicians, Greeks, Romans, Scythians, Gauls, Africans, and others; and was the natural fruit of a religious system, which had for the objects of its worship cruel and merciless divinities. The king of Moab, in this case, sacrificed his son to obtain the favour of Chemosh his god, who, being a devil, delighted in blood and murder, and the destruction of mankind. The dearer any thing was to them, the more acceptable those idolaters thought the sacrifice, and therefore burnt their children in the fire to their honour.
Genesis 22:2 Genesis 22:13 ; Deuteronomy 12:31 ; Judges 11:31 Judges 11:39 ; Psalms 106:37 Psalms 106:38 ; Ezekiel 16:20
Micah 6:7

they departed
1 Samuel 14:36-46 ; 1 Kings 20:13 1 Kings 20:28 1 Kings 20:43