“Unite my heart to fear your name.
I will praise you, O LORD my God, with all my heart.”
You can praise God with all your heart only when nothing from another god is in it. A divided heart is a heart that believes some of what God says and some of what another god says, too.
Most of God’s people believe things Jesus said, but their heart is divided by faith in what one of Christianity's gods says, too. Whether it be a lie from the Baptist god, or from the Methodist god, or the Catholic god, or the Pentecostal god, or one of the many others, it divides the heart. It divides one’s faith between the true God and another one.
A “united heart” is a heart that believes nothing but what God says. Only those whose hearts have been purged by the truth from everything false can glorify God with their whole heart. They may glorify God most of the time, but part of their hearts still belong to the god who taught them the lies they believe.
To pray for a united heart is to pray to know all the truth. May God give each of us a united heart so that we will praise Him with all our hearts!