Charles Ellicott Commentary Leviticus 23:38

"besides the sabbaths of Jehovah, and besides your gifts, and besides all your vows, and besides all your freewill-offerings, which ye give unto Jehovah." — Leviticus 23:38 (ASV)

Beside the sabbaths.—By a figure of speech called metonymy, which is frequently used in both the Old and New Testaments, the expression sabbaths stands here for the sacrifices of the sabbaths, just as in Leviticus 25:6 sabbath of the land denotes the produce of the sabbath of the land, or of the sabbatic year, and as the phrase it is written in the prophets (Mark 1:2) is used for "it is written in the writings of the prophets." (Matthew 7:12; Matthew 22:40, and so on.)

The meaning, therefore, of the passage before us is that the sacrifices ordered for each of these festivals are to be in addition to the sacrifices appointed to each weekly sabbath in the year. Thus, when one of these festivals falls on a sabbath, the sacrifices due to the latter are not set aside by the former. Both must be offered in their proper order.

Beside your gifts.—Nor are they to interfere with the voluntary offerings which each individual brought privately (Deuteronomy 16:10; Deuteronomy 16:17; 2 Chronicles 25:7–8), or with the performance of vows (Deuteronomy 12:6–12).