John Gills Exposition of the Bible Commentary - Genesis 4:3
And in process of time it came to pass ,.... Or "at the end of days" F3 מקץ ימים "in fine dierum", Pagninus, Montanus; "a fine dierum", Schmidt. ; which some understand of the end of seven days, at the end of the week, or on the seventh day, which they suppose to be the sabbath day, these sons of Adam brought their offerings to the Lord: but this proceeds upon an hypothesis not sufficiently established, that the seventh day sabbath was now appointed to be observed in a religious... read more
Matthew Henry's Complete Commentary - Genesis 4:3-5
Here we have, I. The devotions of Cain and Abel. In process of time, when they had made some improvement in their respective callings (Heb. At the end of days, either at the end of the year, when they kept their feast of in-gathering or perhaps an annual fast in remembrance of the fall, or at the end of the days of the week, the seventh day, which was the sabbath)--at some set time, Cain and Abel brought to Adam, as the priest of the family, each of them an offering to the Lord, for the doing... read more