Acts 16:31-33 (NKJV)
So they said, “Believe on the Lord Jesus Christ, and you will be saved, you and your household.” 32 Then they spoke the word of the Lord to him and to all who were in his house. 33 And he took them the same hour of the night and washed their stripes. And immediately he and all his family were baptized.
This morning we have the privilege of welcoming a number of households into membership at Trinity Church. At such times it is always profitable to recall why we do this membership thing. This morning I would like us to consider why we administer membership vows to the Head of Household rather than to each individual member of the household. Why do this?
The point is certainly not that only the Head of Household is important; nor is the point that in order to be a member of the church you have to be an adult. May it never be! It is important to remember that the Head of Household is taking a vow not only for himself or herself but for his or her entire household. In other words, if you have been baptized and you are part of a member household, then you individually are a member of this congregation. You receive the loving care of Christ, the kindly fellowship of the covenant community, and the gracious accountability of the elders and deacons. You are part of the body, an integral member of the covenant community, and to be treated as such. So as we bring these families and individuals forward, all those who have been baptized join us as members of the church.
If they are all individually members of the congregation, then why have just the Head of Household take the vows? The reason is this: to emphasize that God has created a covenantal world. What this means is that not all the decisions which affect us personally and legally are decisions that we ourselves make. All of us were born to parents that we did not choose; we were born into a country we did not choose; we were born subject to laws and statutes we did not choose. Not only is this the case, we all were born in sin, subject to the wrath of God, because of the rebellion of our father Adam. He was our representative, the one whose sin determined the course of our lives. God created the world in such a way that we have representatives whose choices affect us for good and for ill.
And praise God that this is true – for were it not, none of us could ever be saved. Why not? Because we are saved not because of anything we have done but because of Christ. We have His righteousness credited to our account. Though we have not personally been righteous, God in His grace and mercy looks upon us in Christ and treats us as holy and beloved. Because we are part of His house, under His loving headship, we receive innumerable blessings.

So household vows emphasize three things: first, the critical role that the head of household has for the spiritual vitality and health of the entire household. Second, the incredible blessings that come to the entire household when that household is subject to the Lord Jesus Christ. And third, the need for faithfulness from every member of the household so that, in the future, additional healthy, robust, and godly households can be established to the glory of God.