John Gill expounds on Psalm 110:4, emphasizing that Christ is a priest forever after the order of Melchizedek, distinct from the Levitical priesthood due to its imperfections. He illustrates Melchizedek's significance as both king and priest, highlighting that Christ embodies these roles perfectly and eternally. Gill argues that Christ's priesthood is established by God's unchangeable oath, ensuring its everlasting nature and superiority over the Levitical order. He concludes by affirming the importance of recognizing Christ's unique priesthood and the blessings it brings to believers.