Matthew Poole and continuators on Exodus 23:16

16 And the feast of harvest the first-fruits of thy labours , which thou hast sown in the field: and the feast of in-gathering which is in the end of the year , when thou hast gathered in thy labors out of the field.

(i. e.) Of wheat-harvest: for barley-harvest was before this time. This feast was otherwise called Pentecost.

How were these the first-fruits, when a sheaf was offered to God in the feast of the Passeover? Ans. That sheaf was generally of barly, which was less considerable than their wheat, but this was the first-fruits of their wheat, which was their principal grain, and they had no bread before this time from the growth of that year.

To wit, of all the rest of the fruits of earth, as of the vines and olives. This was called also the feast of booths, and of Tabernacles. See Levit. 23. 34. Numb. 29. 12. Deut. 16. 13. All their three feasts had a respect to the harvest, which began in the Passeover, was carried on at Pentecost, and was fully compleated and ended in this feast.

Of the common or civil year which began in September, as the sacred year began in March.