Adam Clarke on Numbers 13:22

Hebron was built seven years before Zoan in Egypt - The Zoan of the Scriptures is allowed to be the Tanis of the heathen historians, which was the capital of Lower Egypt. Some think it was to humble the pride of the Egyptians, who boasted the highest antiquity, that this note concerning the higher antiquity of Hebron was introduced by Moses. Some have supposed that it is more likely to have been originally a marginal note, which in process of time crept into the text; but all the versions and all the MSS. that have as yet been collated, acknowledge it.