In the fourteenth day of this month, at even, ye shall keep it in his appointed season: according to all the rites of it, and according to all the ceremonies thereof, shall ye keep it. According to all the rites of it - See all those rites and ceremonies largely explained in the notes on Exodus 12 (note).
Related Commentaries of Numbers 9:3
Numbers 9:3
3 In the fourteenth day of this month, at even,a ye shall keep it in his appointed season: according to all the rites of it, and according to all the ceremonies thereof, shall ye keep it.