The “word of Christ” refers to Christ’s teachings, both directly as found in the Gospels as well as those explained by the apostles. According to Paul, the teachings of Jesus “live” within believers in a powerful way.
This verse lists three specific applications of Christ’s word dwelling in the life of a believer. The first two aspects are noted together: teaching and admonition. Christ’s word can instruct us, which is “teaching.” At the same time, Christ’s word can also show us where we are right or wrong. “Let the word of Christ dwell in you”
The phrase “the word of Christ” is the only occurrence in the New Testament. The normal way the New Testament phrases the idea of the Bible is “the word of the Lord” or “the word of God.”
Note the word “let.” The word of Christ is ready and willing to dwell in us. The only issue that remains is our volition. The word will indwell us if we let it. God will manufacture the word of Christ in our hearts.
The word “dwell” means to keep house. We should live in the Word of God like we live in our homes. We are familiar with our home, where all the closets are, and where we have items stored. We must thoroughly acquaint ourselves with the Word. The Word should become so familiar to us that we know it like the back of our hand. The idea is to let the Word of Christ dwell inside and live at home in our lives. The Word of God needs to inhabit us. This habitation is more than just reading the Bible. God wants us to let the peace of Christ rule in our hearts (v. 15), and the Word of Christ dwells in our hearts.
Paul encourages the singing of various types of spiritual songs. Paul never gives preference to one type of music over another. His purpose here is simply to state that all types of music were to be used to let the word of Christ dwell richly within us. This singing was to be done with an attitude of thanksgiving. Singing praise to God is largely associated with showing our gratitude to Him, rather than focusing on ourselves or our own desires.