Adam Clarke on 1 Chronicles 3:17

The sons of Jeconiah - Jeremiah has said (Jer 22:30) that Jeconiah, or, as he calls him, Coniah, should be childless; but this must refer to his posterity being deprived of the throne, and indeed thus the prophet interprets it himself: For no man of his seed shall prosper, sitting upon the throne of David, and ruling any more in Judah.

Assir - Salathiel was not the son of Assir, but of Jeconiah, Mat 1:12. Who then was Assir? Possibly nobody; for as the Hebrew אסר assir signifies a prisoner, it may be considered as an epithet of Jeconiah, who we know was a very long time prisoner in Babylon. See 2Kgs 24:15 and Calmet.