The gospel is for the salvation of the lost. This is commanded and clearly taught to us by the Lord Jesus Himself:
And he said to them, “Go into all the world and proclaim the gospel to the whole creation.” (Mark 16:15)
The gospel is also for the nourishment, sanctification and edification of the church. Whole books of the Bible, i.e. Romans, Ephesians, etc., are Gospel-proclaiming epistles plus application, written and sent to local congregations “for teaching, for reproof, for correction, and for training in righteousness” (2 Timothy 3:16).
Think about it, the book of Revelation is pure gospel communication from the Lord Jesus Himself, unveiled, written and sent to comfort and strengthen the persecuted church of the 1st century.
And so, Christians ought to never graduate from the gospel. Instead, we are to sink our roots deeper and deeper in the gospel, constantly growing in our understanding and faith in Christ’s finished work for us on the cross, and thereby flourish and grow in Christ-likeness, and so become more and more consistent, persevering and effective in our witness to the world.
And so we, pastors, ought to dedicate and expend ourselves to the “Lord’s Day after Lord’s Day” serving of solid, sumptuous “law and gospel” feasts for God’s covenant children under our care. It’s the key to church growth, Jesus style.