Charles Ellicott Commentary 1 Chronicles 28:20

"And David said to Solomon his son, Be strong and of good courage, and do it: fear not, nor be dismayed; for Jehovah God, even my God, is with thee; he will not fail thee, nor forsake thee, until all the work for the service of the house of Jehovah be finished." — 1 Chronicles 28:20 (ASV)

And David said to Solomon his son. —The conclusion of the speech begun in 1 Chronicles 28:9–10, and interrupted by the transfer of the plans and designs (1 Chronicles 28:11–19).

Be strong and of good courage. —So 1 Chronicles 22:13. And do is added here, because the time for action is imminent.

Fear not ... forsake thee. —From Deuteronomy 31:6; Deuteronomy 31:8. (See also Joshua 1:5-6.)

My God. —Recalling, in a single word, all his own wonderful experience of the Divine Helper.

Fail. — Drop, let go, and so dismiss, desert.

Until. —The word implies nothing about the time beyond the expressed limit. (Compare to εws, Matthew 1:25.)