Why Jesus could not be used as a sacrifice.

There are several verses that indicate that God is against child sacrifice. God expressly forbids it:

• Deuteronomy 12:31: You must not worship the LORD your God in their way, because in worshiping their gods, they do all kinds of detestable things the LORD hates. They even burn their sons and daughters in the fire as sacrifices to their gods.
• Deuteronomy 18:9-12: When you enter the land the LORD your God is giving you, do not learn to imitate the detestable ways of the nations there. Let no one be found among you who sacrifices his son or daughter in the fire...Anyone who does these things is detestable to the LORD, and because of these detestable practices the LORD your God will drive out those nations before you.

and its practice is described as evil:

• 2 Kings 16:3: He walked in the ways of the kings of Israel and even sacrificed his son in the fire, following the detestable ways of the nations the LORD had driven out before the Israelites.
• Psalm 106:38: They shed innocent blood, the blood of their sons and daughters, whom they sacrificed to the idols of Canaan, and the land was desecrated by their blood.
• Jeremiah 19:4-5: For they have forsaken me and made this a place of foreign gods; they have burned sacrifices in it to gods that neither they nor their fathers nor the kings of Judah ever knew, and they have filled this place with the blood of the innocent. They have built the high places of Baal to burn their sons in the fire as offerings to Baal - something I did not command or mention, nor did it enter my mind.

The OT doesn't prescribe or require human sacrifice. All the rules concerning what sorts of offerings were acceptable for various purposes mention only animals, birds, and grain - humans are never mentioned as an option.