Where did Hevel get the idea to offer an animal?

Question

We know (Bereishit 4) that Hevel kept flocks (not for eating yet, but perhaps for wool and/or milk?), and on that fateful day he offered one to God which Rashi says God consumed in fire. Where did he get the idea to offer an animal in the first place? Or if Adam and Chava offered animals and he learned from them, where did they get the idea?

Nowhere in the text does God call for such offerings and it doesn't seem like an obvious idea. Did they reason somehow that this would be desired by God? Is there midrash in which God does call for korbanot?

(This related question asks how killing an animal was ok before people could eat meat.)

Answer 1

Pirkei d'Rabbi Eliezer Chapter XXI:

Now Cain was a man who loved the ground in order to sow seed and Abel was a man who loved to tend the sheep the one gave of his produce as food for the other, and the latter gave of his produce as food for his (brother, assuming here that Abel gave Cain milk, butter, etc). The evening of the festival of Passover arrived. Adam called his sons and said to them : In this (night) in the future Israel will bring Paschal offerings, bring ye also (offerings) before your Creator.

(Cain) brought the remnants of his meal of roasted grain, (and) the seed of flax, and Abel brought of the firstlings of his sheep, and of their fat, he-lambs, which had not been shorn of their wool.

So Adam informed them of the concept of sacrifice. They brought sacrifices from things that they used for sustenance and consumed, each from what they loved.

(Interestingly enough, we emulate both sacrifices, Abels through offerings of livestock, and Cain's through meal offerings.)

Answer 2

The Ben Ish Chai in his sefer אמרי בינה here says that the reason why Adam and Noach and the Avos brought animal sacrifices was to bring part of themselves as a gift to Hashem through the thoughts that they had when they brought the offering. That is, when they were slaughtering the animal on the altar they imagined that they themselves were being slaughtered and offered up to Hashem, and the power of these thoughts rose up to Hashem and dragged along with them the holy sparks that are intermixed in all parts of Hashem's creation - humans, animals, vegetation and minerals.

This is the gift which a person brings to Hashem with the sacrifices, because imagination alone is not enough to separate the holy sparks - both a physical action together with the thoughts of the imagination are needed, as we see by many mitzvos, for example, tashlich, shofar and lulav. Also, we see many times in the Tanach that the prophets acted out various physical procedures in order to effect certain prophecies.

This elevation of the holy sparks through the thoughts of the imagination that one has when bringing a sacrifice is similar to the elevation of the holy sparks that happen when we imagine giving our lives for the sake of the sanctification of Hashem's name when we recite the word אחד at the end of the first posuk of the Shema, and similarly when we recite Tachanun.

Answer 3

God made the first sacrifice when he made garments for Adam and Chava. By doing this he teached Adam, and Adam transmitted this to his children. The hebrew text says that Hevel and Cayin offered a mincha, and beside this Hevel brought of the first-born (מבכרות) of his flock, and it was by this alone that he acknowledged himself a sinner.