Which month is the first month of the Jewish religious year?
The first month of the Jewish religious year is April. The context explains that the Jewish calendar is arranged so that April serves as the first month of their religious year. This month is when the lamb was taken on the tenth day and kept until the fourteenth day.
Les explains that the Jewish calendar now is set up so that April is the first month of their religious year, though he notes he doesn't like to use the word 'religious' but it's the best fit. In this first month, on the tenth day, every man was to take a lamb according to the house of their fathers, a lamb for a house. If the household was too small for the lamb, they were to share with a neighbor, making sure there was no shortfall. The lamb had to be without blemish, a male of the first year, taken from the sheep or goats, and kept until the fourteenth day of the same month. Les points out this is a beautiful illustration of the Lord Jesus, who was without spot, without blemish, without sin. To prove He was spotless and sinless, He ministered three years.
This month shall be unto you the beginning of months: it shall be the first month of the year to you.