Charles Ellicott Commentary Deuteronomy 9:2

"a people great and tall, the sons of the Anakim, whom thou knowest, and of whom thou hast heard say, Who can stand before the sons of Anak?" — Deuteronomy 9:2 (ASV)

Whom thou knowest. —The pronoun is emphatic. The twelve spies, two of whom were still living, had seen them (Numbers 13:33), and their fame was doubtless notorious. It seems to have been a common saying, possibly among the Anakim themselves, “Who will stand up to the children of Anak?” No one could be found to face them.