Matthew Poole and continuators on Joshua 8:30

30 Then Joshua built an altar unto the LORD God of Israel in mount Ebal .

To wit, after the taking of Ai. For they were obliged to do this, when they were brought over Iordan into the Land of Canaan, Deut. 11. 29. and 27, 2, 3. which is not to be understood strictly, as if it were to be done the same moment or day; for it is manifest they were first to be Circumcised, and to eat the Passover, which they did, and which was the work of some days; but as soon as they had opportunity to do it, which was now when these two great Frontier Cities were taken and destroyed, and thereby the Coast cleared, and the bordering people under great consternation and confusion, that all the Israelites might securely march thither. And indeed this work was fit to be done as soon as might be, that thereby they might renew their Covenant with, and profess their subjection to that God by whose help alone they could expect Success in their great and difficult enterprise.

To wit, for the Offering of Sacrifices, as appears from the following verse, and from Deut. 27. 5, 6, 7.

Why not on Mount Gerizim also? Ans. Because Gods Altar was to be but in one place, Deut. 12. 13, 14. and this place was appointed to be Mount Ebal, Deut. 27. 4, 5. which also seems most proper for it, that in that place whence the Curses of the Law were denounced against Sinners, there might also be the tokens and means of Grace, and Peace, and Reconciliation with God, for the removing of the Curses, and the procuring of Gods Blessing unto Sinners.