||This month shall be the head month to you. It shall be the first month of the year.
Hachodesh hazeh lachem rosh chodashim rishon hu lachem lechodeshey hashanah.
||Speak to the entire community of Israel, saying: On the tenth of this month, every man must take a lamb for each extended family, a lamb for each household.
Daberu el-kol-adat Yisra'el lemor be'asor lachodesh hazeh veyikchu lahem ish seh leveyt-avot seh labayit.
Nissan. This occurs in March and April.
|first month of the year|
This is seen as a commandment to maintain a calendar (Rosh HaShanah 18a; Sanhedrin 11a; Sefer HaMitzvoth; Positive Commandment 193). The calendar is lunar in nature, with an occasional leap-month added to keep it in conformity with the solar year.
|tenth of this month|
This was only required for the first Passover in Egypt, but not subsequently (Pesachim 96a; Rashi).
The Hebrew word seh here can denote any young of the small ruminants, and can thus refer either to a lamb or to a kid, as we seen in Exodus 12:5.
See Exodus 6:14, Numbers 1:2, 17:17 (Mekhilta; Pesachim 96a; Rashi; Hirsch).