Charles Ellicott Commentary Ezra 6:10

"that they may offer sacrifices of sweet savor unto the God of heaven, and pray for the life of the king, and of his sons." — Ezra 6:10 (ASV)

That they may offer sacrifices ... and pray for the life of the king. —Two ends are to be answered: the God of heaven is to be honoured, and the dynasty of Darius interceded for by the Jews .

Of sweet savours. —The word occurs again only in Daniel 2:46, and there is translated “sweet odours,” meaning incense. The connection of this with the prayer following justifies the same translation here, and, moreover, indicates under what good instruction the decree was drawn up.