The Psalms were the prayer and songbook for the early Church and many Psalms begin with calling God’s people together to worship Him (Ps. 34:1-3; 95:1-7; 100; etc.). This marks off the gathering for the purpose of worship and distinguishes it from other assemblies of people. It also orients God's people to the fact that they are now in a solemn service and their hearts and thoughts are to be trained upon Him.