Jamieson, Fausset and Brown on Isaiah 51:16

16. Addressed to Israel, embodied in "the servant of Jehovah" (Is 42:1), Messiah, its ideal and representative Head, through whom the elect remnant is to be restored.

put my words in thy mouth--true of Israel, the depository of true religion, but fully realized only in Israel's Head and antitype, Messiah (Is 49:2; 50:4, 5; 59:21; De 18:18; Joh 3:34).

covered ... in ... shadow of ... hand--protected thee (see on Is 49:2).

plant--rather, "fix" as a tabernacle; so it ought to be rendered (Da 11:45). The "new creation," now going on in the spiritual world by the Gospel (Ep 2:10), and hereafter to be extended to the visible world, is meant (Is 65:17; 66:22; compare Is 13:13; 2Pe 3:10-13).

Zion--Its restoration is a leading part in the new creation to come (Is 65:17, 19).