Charles Ellicott Commentary Ezra 4:2

"then they drew near to Zerubbabel, and to the heads of fathers` [houses], and said unto them, Let us build with you; for we seek your God, as ye do; and we sacrifice unto him since the days of Esar-haddon king of Assyria, who brought us up hither." — Ezra 4:2 (ASV)

As you do. —They feared the Lord, and worshipped their own gods (2 Kings 17:33): thus they came either in the spirit of hypocrites or with an intention to unite their own idolatries with the pure worship of Jehovah. In any case, they are counted enemies of the God of Israel.

We do sacrifice to Him since the days of Esar-haddon. —He ended his reign B.C. 668, and therefore the Samaritans speak from a tradition extending backwards a century and a half.

Which brought us up here. —Thus they entirely leave out of consideration what residue of Israel was still to be found among them.