Albert Barnes Commentary Numbers 24:23

"And he took up his parable, and said, Alas, who shall live when God doeth this?" — Numbers 24:23 (ASV)

When God does this - The eventual carrying away of the allies of Israel by Assyria presented itself to Balaam as the ruin of all peace and safety on earth. One prediction, however, was still lacking, and is next given, namely, that the conquerors of the Kenites should fare no better than the Kenites themselves.