Genesis 3:21

We have here a further instance of God's care concerning our first parents, notwithstanding their sin. Though he corrects his disobedient children, and put them under the marks of his displeasure, yet he does not disinherit them, but, like a tender father, provides the herb of the field for their food and coats of skins for their clothing. Thus the father provided for the returning prodigal, Luk 15:22, Luk 15:23. If the Lord had been pleased to kill them, he would not have done this for them. Observe, 1. That clothes came in with sin. We should have had no occasion for them, either for defence or decency, if sin had not made us naked, to our shame. Little reason therefore we have to be proud of our clothes, which are but the badges of our poverty and infamy. 2. That when God made clothes for our first parents he made them warm and strong, but coarse and very plain: not robes of scarlet, but coats of skin. Their clothes were made, not of silk and satin, but plain skins; not trimmed, nor embroidered, none of the ornaments which the daughters of Sion afterwards invented, and prided themselves in. Let the poor, that are meanly clad, learn hence not to complain: having food and a covering, let them be content; they are as well done to as Adam and Eve were.

— Matthew Henry's Concise Commentary (public domain)

God made coats of skins--taught them to make these for themselves. This implies the institution of animal sacrifice, which was undoubtedly of divine appointment, and instruction in the only acceptable mode of worship for sinful creatures, through faith in a Redeemer (Heb 9:22).

— Jamieson-Fausset-Brown Commentary (public domain)