Deuteronomy 23:6 - Matthew Poole's English Annotations on the Holy Bible

i.e. Make no contracts, either by marriages, or leagues, or commerce with them, but rather shalt constantly keep a jealous eye over them, as enemies who will watch every opportunity to insnare or disturb thee. This counsel was now the more necessary, because a great part of the Israelites lived beyond Jordan in the borders of those people, and therefore God sets up this wall of partition betwixt them, as well knowing the mischief of bad neighbours, and Israel's proneness to receive infection from them. Each particular Israelite is not hereby forbidden to perform any office of humanity to them, but the body of the nation are forbidden all friendly and familiar conversation with them.