First Timothy 5:21 mentions "elect angels." No matter how a person views the specifics of election, it is clear that God is somehow involved in choosing who will be saved. And it seems He also elects certain angels who would not sin.
Could more of the angels sin?
His sovereign decisions are found throughout Scripture. God chose Abram as the father of the nation of Israel (Genesis 17:1–4). He chose Mary as the mother of Jesus (Luke 1:30–31). God chose Paul to bring the Gospel to the Gentiles, as He told Ananias in a vision: "But the Lord said to him, 'Go, for he is a chosen instrument of mine to carry my name before the Gentiles and kings and the children of Israel'" (Acts 9:15). The Bible also talks about believers as being "chosen" by God. Ephesians 1:3–4, for example, says, "Blessed be the God and Father of our Lord Jesus Christ, who has blessed us in Christ with every spiritual blessing in the heavenly places, even as he chose us in him before the foundation of the world, that we should be holy and blameless before him." First Peter 2:9 says, "But you are a chosen race, a royal priesthood, a holy nation, a people for his own possession, that you may proclaim the excellencies of him who called you out of darkness into his marvelous light."
When it comes to the angels, it appears that God gave them a one-time choice. Those who followed Satan cannot repent and turn to God. Those who did not follow Satan have remained loyal to God and are secure in that decision. The Bible gives us no reason to believe that more angels could sin.
What are angels according to the Bible?
When were the angels created?
Are demons and fallen angels the same thing?
Why did God allow the Satan and the demons to sin?
When Lucifer / Satan fell, did one third of the angels fall with him?
Truth about Angels