Deuteronomy 12:6 - Albert Barnes' Notes on the Bible

Some have objected that this command cannot possibly have been ever carried out, at all events until in later (lays the territory which owned obedience to it was narrowed to the little kingdom of Judah. But in these and in other precepts Moses doubtless takes much for granted. He is here, as elsewhere, regulating and defining more precisely institutions which had long been in existence, as to many details of which custom superseded the necessity of specific enactment. No doubt the people well understood what Maimonides expressly tells us in reference to the matter, namely, that where immediate payment could not be made, the debt to God was to be reserved until the next great Feast, and then duly discharged. The thing especially to be observed was that no kind of sacrifice was to be offered except at the sacred spot fixed by God for its acceptance.