ROMANS 4:21 Fully satisfied and assured that God was able and mighty to keep His Word and to do what He had promised. Amp.
DEFINITIONS
Assure -d) to make a person sure of something: convince. To give confidence to; to make a doubtful thing certain.
We know that Abraham is a very good a example for us to follow. He did not always get it right but He trusted God and that was made righteousness. He was not always confident and assured but had to learn as we do. How did He learn? It says in verse 20 that he grew strong and was empowered by faith as he gave praise and glory to God.
We know he did not only praise God on Sundays. So, he must have made other arrangements. He did not have electricity to play music. So, he may have had instruments. Maybe he just spoke to the Lord. What is important is how we do it and that we do it. God inhabits the praises of His people.
Colossians 3:16 Let the word spoken by the Christ, the Messiah have its home in your hearts and minds and dwell in you in all richness, as you teach and admonish and train one another in all insight and intelligence and wisdom (in all spiritual things and sing) psalms and hymns and spiritual songs, making melody to God with His grace in your hearts.
We see that we must let the words of Jesus dwell in us. We are to teach each other. We are to sing and make melody to God. As we come to Him and sing and teach, we learn and experience who He is, and the end result will be that we too are assured that He is able and mighty to keep His Word and do what He promised.

Amen 🙏🏾 🩷. What a mighty God we serve. Keeping covenants of mercy to those who love him and call on his name. 😊