You are also to keep the Feast of Harvest with the firstfruits of the produce from what you sow in the field. And keep the Feast of Ingathering at the end of the year, when you gather your produce from the field.
God commanded the land to rest every seventh year to show Israel both His abundance and their dependence on Him alone. This was no mercy to the soil but a test of their obedience in the very matter that touches their purse, whether they would trust His Providence as surely as the sixth day's manna served for two days' meat.
AI summary
Commenting on Exodus 23:10-19
Thou shall not offer the blood of my sacrifice with leavened bread,.... This belongs to the feast of the passover; for, as all the Jewish writers agree, this sacrifice is the sacrifice of the passover, as it is sometimes called, see Exo 12:27 now when the paschal lamb was killed, and its blood shed, and its flesh eaten, there was to be no leaven along...
And the feast of harvest, the firstfruits of thy labours, which thou hast sown in the field: and the feast of ingathering, [which is] in the end of the year, when thou hast gathered in thy labours out of the field. (h) Which is Whit Sunday, in token that the law was given 50 days after they departed from Egypt.