There are examples both of public prayer being modeled and public prayer being discouraged in the Bible. The key issue is not whether prayers are said out loud or in public, but the heart of the one praying.
Is praying out loud okay?
Jesus contrasted the public prayers of hypocrites with His instruction that His disciples should pray in private (Matthew 6:5–6). The hypocrites prayed aloud to garner attention and appear righteous before others. Jesus wanted His followers to pray to be seen by the Father, not by others. Jesus often withdrew to private places to pray, but Jesus Himself prayed out loud at times (John 11:41–42; 17). He also taught His disciples how to pray (Matthew 6:5–13), even modeling words with communal requests. His disciples also prayed publicly, out loud (Acts 8:14–15; 16:25; 20:36). The early church gathered to pray together often (Acts 1:14, 24; 2:42).
When the Bible discourages public prayer it is not condemning the action of praying out loud or even publicly, but a self-righteousness or boastful attitude of the person praying. For example, in Luke 18:9–14, Jesus contrasts the prayer of a Pharisee with that of a tax collector. The Pharisee stood in the midst of people at the temple and thanked God that he was not like the sinners he observed. The tax collector stood off at a distance and asked God for mercy. Jesus said that the tax collector "… went down to his house justified, rather than the other. For everyone who exalts himself will be humbled, but the one who humbles himself will be exalted" (Luke 18:14). Both prayers were out loud. The problem, Jesus says, is not the location or the proximity to others when the prayer is uttered, but in the attitude of the Pharisee.
In Luke 20:46–47, Jesus says the scribes who make long prayers for "pretense" and arrange to do good things so they are seen and honored by others, will only gain condemnation. Our relationship with God is to be a holy and intimate one, not one to be flaunted or held aloft for others to admire.
This is not to condemn praying together or praying out loud in public, for there are many examples of the people of God coming together to pray. Rather, it is to say that we must examine our hearts and motives when we pray publicly. Are we doing it for our own benefit or to appear righteous to the crowd, or are we truly coming before our heavenly Father and seeking Him with humble hearts in prayer?
When we gather together to pray, as we should, our aim should be to honor God and speak of His goodness, provision, and mercies, not our own. Ephesians 5:18–21 encourages, ". . . be filled with the Spirit, addressing one another in psalms and hymns and spiritual songs, singing and making melody to the Lord with your heart, giving thanks always and for everything to God the Father in the name of our Lord Jesus Christ, submitting to one another out of reverence for Christ."
What does the Bible say about public prayer? Is it okay to pray in public?
Is silent prayer biblical?
What is the importance of praying for others?
What types of prayer are mentioned in the Bible?
What is the importance of daily prayer in the life of a Christian?
Truth about Prayer