John Gill Commentary Joshua 22:26

"Therefore we said, Let us now prepare to build us an altar, not for burnt-offering, nor for sacrifice:" — Joshua 22:26 (ASV)

Therefore we said
One to another, in order to prevent the apostasy of our children from God, their departure from his worship, and going into idolatry:

let us now prepare to build us an altar ;
get materials ready, and set about it instantly, without any delay, while the thing dwells upon our minds:

not for burnt offering, nor for sacrifice ;
not for offerings of any kind required by the law, neither for sin offerings nor trespass offerings, nor any other not named.