How do we know that Colossians 3:16 and Ephesians 5:19, in regards to singing, are dealing with a congregational worship assembly?
"Therefore be careful how you walk, not as unwise men but as wise, making the most of your time, because the days are evil. So then do not be foolish, but understand what the will of the Lord is. And do not get drunk with wine, for that is dissipation, but be filled with the Spirit, speaking to one another in psalms and hymns and spiritual songs, singing and making melody with your heart to the Lord; always giving thanks for all things in the name of our Lord Jesus Christ to God, even the Father; and be subject to one another in the fear of Christ" (Ephesians 5:15-21).
"Let the peace of Christ rule in your hearts, to which indeed you were called in one body; and be thankful. Let the word of Christ richly dwell within you, with all wisdom teaching and admonishing one another with psalms and hymns and spiritual songs, singing with thankfulness in your hearts to God. Whatever you do in word or deed, do all in the name of the Lord Jesus, giving thanks through Him to God the Father" (Colossians 3:15-17).
How do we know that Paul is speaking of worship? The speaking in psalms, hymns, and spiritual songs is directed to the Lord and is done so to give thanks to God. Worship is doing those things which give praise and honor to God in a manner prescribed by God and with a proper attitude focused on God (John 4:21-24). All parts of the definition of worship are demonstrated in this passage, thus the inescapable conclusion is that we are talking about worship. [See the lesson "What is Worship?" for further information.]
How do we know it is congregational worship? Both passages emphasize that singing is to teach each other, those we are talking about times when the church is gathered together. "What is the outcome then, brethren? When you assemble, each one has a psalm, has a teaching, has a revelation, has a tongue, has an interpretation. Let all things be done for edification" (I Corinthians 14:26). In addition, notice that Ephesians 5:19 is actually in the middle of a sentence that ends with an encouragement for us to be subject to one another. That is followed by a discussion of how the church is subject to Christ (Ephesians 5:25ff). The passage in Colossians follows a verse that means that we are called into one body, which is the church, and so we are to be thankful. Paul then follows it with a command to sing with thankfulness to God.