Adam Clarke on Nehemiah 13:4

Eliashib the priest - Perhaps this was a different person from Eliashib the high priest; but there is no indubitable evidence that he was not the same. If he was high priest, he was very unfaithful to the high charge which he had received; and a reproach to the priesthood. He had married his grandson to Sanballat's daughter: this produced a connection with Tobiah, the fast friend of Sanballat; in whose favor he polluted the house of God, giving him one of the chambers for his ordinary residence, which were appointed for the reception of the tithes, oblations, etc., that came to the house of God.