Psalms 51:16

You do not delight in sacrifice, or I would bring it;

you do not take pleasure in burnt offerings.

(v16, NIV)

Why wouldn't God delight in sacrifice? David is certainly willing to offer it, but he seems to know that God would not be pleased with a burnt offering. God certainly instructs and teaches about burnt offerings in the Old Testament. If they were described and instructed in the Old Testament, why and for what reason would they be there if God does not delight in them? God doesn't even take pleasure in them. What is the purpose of it then? Whether God delights in it or not, there must be a reason behind him instructing it. You may not like lighters, but you may use one to light a candle on a birthday cake to celebrate someone's birthday. In the same way, we get an insight into God and his purposes, seeing that it isn't the sacrifice but something else that God cares about. Therefore, we can't just go around offering sacrifices to God aimlessly and purposelessly expecting God to be pleased with what we're doing.