Why will every Jew that God has ordained for the Kingdom certainly enter it?
Every Jew ordained for the Kingdom will certainly enter because the Sovereign God has decreed it, and God has spoken it. Not one whom He has ordained to go in will miss it; each will find his place in it. The certainty rests on God's sovereign decree, not human effort.
Les explains that the certainty is because this is the Sovereign God. Not a single Jew that is ordained to go into the Kingdom is going to miss it; everyone God has ordained to go into the Kingdom is going to find His place in it. The reason it is certain is that God has spoken it.