John Gill Commentary Ezra 4:20

"There have been mighty kings also over Jerusalem, who have ruled over all [the country] beyond the River; and tribute, custom, and toll, was paid unto them." — Ezra 4:20 (ASV)

There have been mighty kings also over Jerusalem, which have
ruled over all countries beyond the river
As David and Solomon; and the account of these they had in their records, see (2 Samuel 8:1) (1 Kings 4:21 1 Kings 4:24)

and toll, tribute, and custom, was paid unto them ;
as appears from the places referred to; and this served to strengthen the insinuation made to the king, that if these people were suffered to go on building, he would lose his tribute and taxes in those parts.