2 Kings 3:26-27 "And when the king of Moab saw that the battle was too fierce for him, he took with him seven hundred men who drew swords, to break through to the king of Edom, but they could not. Then he took his eldest son who would have reigned in his place, and offered him as a burnt offering upon the wall."
"Then he took his eldest son...and offered him as a burnt offering"
"He took his eldest son and...offered him"
Offering human sacrifices was a very ancient custom, and has been practiced at different times and among many nations, since the most ancient of times. Among the list of nations were the Ethiopians, the Babylonians, the Assyrians, the Phoenicians, the Canaanites, the Scythians, the Egyptians, the Chinese, the Persians, the Indians, the Gauls, the Carthaginians, the Britons, the Arabians, the Romans, and many more, including the Africans and peoples of the Americas.
These sacrifices were offered in many different ways. Most were slaughtered under the knife; some were burned; some were drowned; some were buried alive, some were pushed down the stairs of a massive pyramid temple. In many ancient cultures parents would sacrifice their own children.
The northern kingdom of Israel followed the practices of the surrounding nations throughout all of their years, but whether or not human sacrifice was customary among them or any of the early Israelites there is no proof. Yahweh condemned such practices. The sacrifice of the firstborn was indeed customary with the people of Canaan. In times of of trouble they offered their best and dearest to the gods, 'the fruit of their body for the sin of their soul' (Mic 6:7).
The Old Testament reveals that Ahaz 'made his son to pass through the fire,' this is the incident in Scripture that made the valley of Tophet an abomination as recorded in Jer 7:31-32:
"And they have built the high places of Tophet, which is in the Valley of the Son of Hinnom, to burn their sons and their daughters in the fire, which I did not command, nor did it come into My heart. Therefore behold, the days are coming," says the LORD, "when it will no more be called Tophet, or the Valley of the Son of Hinnom, but the Valley of Slaughter; for they will bury in Tophet until there is no room."
Although it is true that Abraham was asked by the Lord to offer his only son on an altar, the Bible indicates that it was a "test" of his faith. Robertson makes a good side note in his book (The Early Religion of Israel, p. 254):
"To Abraham, not unfamiliar with various ways in which among his heathen ancestors the deity was propitiated, the testing question comes, 'Art thou prepared to obey thy God as fully as the people about thee obey their gods?' and in the putting forth of his faith in the act of obedience, he learns that the nature of his God is different. Instead, therefore, of saying that the narrative gives proof of the existence of human sacrifice as an early custom in Israel, it is more reasonable to regard it as giving an explanation why it was that, from early time, this had been a prime distinction of Israel that human sacrifice was not practiced as among the heathen."
Phoenician mythology records that when war and pestilence afflicted the land, a man named Krones offered up his son Yeoud as a sacrifice.
note: An interesting inscription discovered near ancient Babylon contained an offer of Nebuchadnezzer allowing his son to be burned to death to assure his nation's protection.
Bibliography on Ancient Customs
The Art of Ancient Egypt, Revised by Robins, 272 Pages, Pub. 2008