John Gill emphasizes the importance of reminding believers of their duties and responsibilities in Christ, as he reflects on his role as an apostle and elder. He likens the human body to a temporary tabernacle, underscoring the transient nature of life and the urgency to live out one's faith actively. Gill points out that Christians often forget their obligations and become sluggish in their spiritual walk, hence the need for constant reminders to stir them up to action.