The first month on the Hebrew calendar, called Nisan (from the Babylonian calendar), the seventh civil month, today. It is the first month of the year, according to the Torah, and is the month of the first fruits and of Passover. Abib/Nisan occurs in March–April on the Gregorian calendar.
See 2 Moses 23:13; 3 Moses 33:13, 39:13, 40:1, 50:1; 4 Moses 1:1, 8:9, 9:1-4; 5 Moses 14:1-4; Exodus 12:1-2.