John Gill expounds on 1 John 5:6, emphasizing that Jesus Christ came by both water and blood, signifying His baptism and sacrificial death. He clarifies that the 'water' refers to the ordinance of baptism, which revealed Christ as the Son of God, while the 'blood' signifies His atoning sacrifice for humanity's sins. Gill highlights that Christ's manifestation as the Son of God was evident not only at His baptism but also at His crucifixion, where His blood cleanses from sin. The sermon also discusses the role of the Holy Spirit as a witness to Christ's divine nature and truth. Ultimately, Gill underscores the importance of recognizing Jesus as the embodiment of truth through the Spirit.