So says Peter Adam, in his book Speaking God’s Words (p131).

A ministry sentence is a summary of the sermon, its main point.  It summarises my ministry to the congregation, is expressed in terms of the expected response, and includes an element of appeal or challenge.  It is characteristically expressed in terms of doing, rather than just knowing.  If my sermon is on 1 Corinthians 6:12-20, for instance, I do not just want people to know that sexual immorality is wrong.  I want them to run away from it!  My ministry sentence, the focus and purpose of my sermon, is ‘Flee immorality!’  In a sermon on Galatians 4:12-5:1, it is ‘Stand firm in freedom!’  My ministry sentence helps me to focus my sermon, and helps my hearers to know what the sermon is about.  It is a call, an appeal, to action and response.  I settle on the ministry sentence (and it takes a long time!) by asking myself: ‘What is God saying to this congregation through this text?’ and ‘What response does he want them to make?’  A ministry sentence helps me to apply the teaching.