Therefore said we, that it shall be, when they should so say to us or to our generations in time to come, that we may say again, Behold the pattern of the altar of the LORD, which our fathers made, not for burnt offerings, nor for sacrifices; but it is a witness between us and you.
So, we said that when they tell us or our future generations this message, we will reply by showing them the design of the Lord's altar created by our ancestors. It was not meant for regular offerings or sacrifices, but serves as proof between us and them.