This month shall be unto you the beginning of months: it shall be the first month of the year to you.
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Ambrose of Milan
In like manner also we can understand this statement: “This month shall be to you the beginning of months.” This statement is to be interpreted in reference to time. There is reference to the pasch of the Lord, which is celebrated at the beginning of spring. Therefore he created heaven and earth at the time when the months began, from which time it is fitting that the world took its rise. Then there was the mild temperature of spring, a season suitable for all things. .
Year, sacred or ecclesiastical, which is most commonly used in Scripture. The civil year commenced with Tisri, in September, and regulated the jubilee, contracts (Cornelius a Lap ide)
January was the first month to determine the age of trees, and August to decide when cattle became liable to be tithed. (Chap. xxii. 29; Leviticus xix. 23.) (Calmet)
Before the captivity, the months were not styled Nisan, but abib, (chap xiii. 5,) the first.Bul the 11th, (1 Kings vi.) Sa.
Consequently our elders decided that one full month must be observed for the birthday of the world and that Easter should be observed in whatever part of it both the day and the moon coincided. This is not without scriptural authority, for Moses said, “This month shall stand at the head of your calendar, the first month of the year.” With these words he consecrated a whole month for the day of the world’s birth. Thus our elders, who had found that March was the birthday of the world, defined April as a limit in determining the first month. So it will be permitted to celebrate Easter neither before March nor after April But when during this month both the moon and the day coincide, that is, the fourteenth day of the moon and Sunday, then Easter is to be celebrated. Now again, since the fourteenth day of the moon frequently does not fall on Sunday, they preferred to have the moon extended for seven days, provided they observed Sunday in the joy of the resurrection. So when the day fal...