Since, in Jesus' famous conversation with Nicodemus in John 3 (the passage where we get "for God so loved the world that he gave his only begotten Son..."), Jesus said to him that no one can see the kingdom of God without being born again, Wesley asserts in the beginning of this sermon that it's really important for us to know exactly what that phrase means. He also equates being born again with other similar phrases in Scripture: being born of God and being born of the Spirit.
He then goes on to describe the three defining characteristics of those who have been born of God: their lives display faith, hope, and love. Faith is both a belief in things that are true about Christ and a personal conviction of their effects upon each of us as individuals; hope is assurance from the Holy Spirit that we are God's children we have joy now and a joyous future to look forward to; love is the greatest of all, and consists of our love for God and for everyone around us, and results in a life of total obedience to God's commandments and desires.
The sermon concludes with a very straightforward challenge to Wesley's hearers to examine whether or not these characteristics were truly part of their lives, or if they were resting too heavily upon past obedience to God (particularly their baptism).
The content of this sermon is similar to that of his previous sermon, Sermon 17: Circumcision of the Heart. Both sermons offer descriptions of faith, hope, and love as defining characteristics of true Christians. In Circumcision of the Heart, he also included humility in his list.
To dig in further: