Bede

And Cain was very angry, and his countenance fell. How did Cain know that the Lord had looked favorably upon Abel and his offerings, but had turned away his face from himself and his offerings, unless, as some have interpreted, the Lord had set fire to Abel and his sacrifice, but had not set fire to Cain and his sacrifice, that is, by sending fire from the heavens, He accepted Abel's offering, as we often read that this happened to holy men who offered. Cain, on the other hand, had to consume his own sacrifice by fire. …

Commentary on Genesis (Hexaemeron) ↗