What does it mean to set to his seal that God is true?

In the sermon, the concept of 'setting to his seal' is explained as the act of affirming the truth of God’s word and His promises. When believers receive the testimony of Christ, they validate the truth that only God, through His sovereign work, can bring a person to faith. This aligns with Revelation 7:3, indicating that God’s chosen are sealed for protection and eternity. Thus, believers’ faith acts as an outward expression of the inward reality of being sealed by the Holy Spirit, signifying their belonging to God and His truth.