"Ask, and it will be given to you; seek, and you will find." (Matt. 7:7)
There are so many prayers in a worship service: opening prayers, closing prayers, prayers of confession, the "pastoral prayer" (which can often become quite long!), prayer after the offering, prayer before the sermon, and then prayer after the sermon. Why so many prayers?
The fact that we take so much time for prayer during worship indicates the blunt truth that without the blessing of Christ we can do nothing (John 15:5). It also indicates that we know that everything we have comes from God, so we are to be thankful in everything (Phil. 4:6).
We use the term prayer of invocation as a formal term to describe the first prayer in a Lord's Day worship service. (In our church, we usually call it the "prayer for God's blessing on our worship.") It may well be the most important prayer of any worship service.
In a prayer of invocation, we "invoke" (i.e., call upon, summon, beg) God to bless our time of worship. While God greets us as we gather (in the salutation), we do not presume upon his promised mercy to us. We praise God for who he is. (Notice that the elements of a prayer of invocation usually include things about which we have just sung or confessed.) We earnestly ask God to use the means of grace as means of grace to those who are present.
Among other things, we pray that: