There are good reasons for believing that in pre-Mosaic times the day of new moon was celebrated by the Israelites and all kindred peoples, as it is still among certain heathen races. Originally a nature festival, it was consecrated to Jehovah by the legislation before us, and gradually became of account as the occasion of domestic gatherings and rejoicings. But its religious significance lay chiefly in the dedication to God of the month that had begun and expiation of guilt contracted during that which had closed.

We come now to the great annual festivals. These were arranged in two groups, which may be classed as vernal and autumnal, the one group belonging to the first and third months, the other to the seventh. They divided the year into two portions, the intervals between them being the time of great heat and the time of rain and storm. The month Abib, with which the year began, corresponded generally to our April; but its opening, depending on the new moon, might be earlier or later. One of the ceremonies of the festival season of this month was the presentation, on the sixteenth day, of the first sheaf of harvest; and seven weeks afterwards, at Pentecost, cakes made from the first dough were offered. The explanation of what may appear to be autumnal offerings in spring is to be found in the early ripening of corn throughout Palestine. The cereals were all reaped during the interval between Passover and Pentecost. The autumnal festival celebrated the gathering in of the vintage and fruits.

The Expositor's Bible:The Book of Numbers — Part 201

The Passover, the first great feast, a sacrament rather, is merely mentioned in this portion of Numbers. It was chiefly a domestic celebration--not priestly--and had a most impressive significance, of which the eating of the lamb with bitter herbs was the symbol. The day after it, the "feast of unleavened bread" began. For a whole week leaven was to be abjured. On the first day of the feast there was to be a holy convocation, and no servile work was to be done. The closing day likewise was to be one of holy convocation. On each of the seven days the offerings were to be two young bullocks, one ram, and seven yearling he-lambs, with their meal and drink offerings, and for sin one he-goat to make atonement.

The Expositor's Bible:The Book of Numbers — Part 201