John Gill Commentary Joshua 22:27

"but it shall be a witness between us and you, and between our generations after us, that we may do the service of Jehovah before him with our burnt-offerings, and with our sacrifices, and with our peace-offerings; that your children may not say to our children in time to come, Ye have no portion in Jehovah." — Joshua 22:27 (ASV)

But [that] it [may be] a witness between us and you, and our
generations after us
That we are one people, worship one God, and serve at one altar, of which this built was a resemblance, and would put them in mind of it:

that we might do the service of the Lord before him ;
in the tabernacle, and at the altar, in the place where he had chosen to put his name and dwell:

with our burnt offerings, and with our sacrifices, and with our peace
offerings ;
to be brought at stated times, or as occasion required:

that your children may not say to our children, in time to come, you
have no part in the Lord ;
nor right to his altar, and so forbid them offering their sacrifices on it; or "have no part in the Word of the Lord," as the Targum; the Messiah, whose sacrifice was typified by the sacrifices of the legal dispensation, and all such, who offered theirs in the faith of that, had a part in it, and their sins were expiated by it.