Matthew Poole and continuators on 2 Kings 3:27

27 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.

Either, First, the King of Edom's Son; whom in his eruption he took, and then Sacrificed. Compare Amos 2. 1. But, First, That place speaks of the king, not of the kings son▪; and of the burning of his bones, not of the offering of a living man for a Burnt-Offering. Secondly, This would not have made the besiegers to raise their siege, but to have followed it more warmly to revenge so barbarous an action. Thirdly, The following clause, that should have reigned in his stead, agrees not so well to the Edomites, whose King was onely Iehoshaphat's Vice-Roy, and therefore his Son had no right to succeed him; as it doth to the Moabites, whose King was revolted from Israel, and intended to keep that Kingdom to himself and Children. Or rather, Secondly, His own Son: whom he Sacrificed; partly, to obtain the favour of his God, according to the manner of the Phoenicians and other people in grievous and publick Calamities; whereof we have manifest testimonies, both in Scripture, as Ps. 106. 37. Ezek. 20. 31. and in Heathen Authors, as Porphyrius, Plutarch and others: and partly, to oblige the Israelites to quit the siege out of compassion; or, as despairing to Conquer (at least without greater loss of men than it was worth) him who was resolved to defend himself and City to the utmost extremity.

That the besiegers might see it, and be moved by it.

Or, great trouble or repentance upon Israel, i. e. the Israelitish King and people (who was the first cause of the War, and had brought the rest into confederacy with him) were greatly afflicted and grieved for this barbarous action, and resolved to prosecute the War no further, and so withdrew their Forces, as also did their Allies, and returned to their several Homes. Which they were the more willing to do, because the Kingdom and Countrey of Moab were so ruinated both as to their Men, and Cities, or Villages, and Lands, that they were all secure of any great annoyance from it.

Marginal references: Amos 2. 1.; Heb. great repentance upon Israel.