Albert Barnes Commentary Ezekiel 9:3

"And the glory of the God of Israel was gone up from the cherub, whereupon it was, to the threshold of the house: and he called to the man clothed in linen, who had the writer`s inkhorn by his side." — Ezekiel 9:3 (ASV)

Cherub - The singular is put collectively for the “cherubim,” which were upon the mercy-seat of the ark in the Holy of Holies, the proper seat of the glory of the Lord in the midst of Israel. God is represented as “arising” from between the cherubim to scatter His enemies (Numbers 10:35).