John Gill Commentary Ezra 4:18

"The letter which ye sent unto us hath been plainly read before me." — Ezra 4:18 (ASV)

The letter which you sent to us
The plural number is used, being now become courtly for kings thus to speak of themselves:

has been plainly before me ;
by such that understood both the Syrian and Persian languages; the letter was written in the Syrian language, and the king being a Persian, it was necessary it should be interpreted and explained to him.