But although you may be born again, it will require time to become a full-grown Christian. Justification is instantaneous; but sanctification is a lifework. We are to grow in wisdom. Peter says “Grow in grace, and in the knowledge of our Lord and Saviour Jesus Christ” (2 Peter 3:18); and in the first chapter of his Second Epistle, “Add to your faith virtue; and to virtue knowledge; and to knowledge temperance; and to temperance patience; and to patience godliness; and to godliness brotherly kindness; and to brotherly kindness charity. For if these things be in you and abound they make you that ye shall neither be barren nor unfruitful in the knowledge of our Lord Jesus Christ.” So that we are to add grace to grace. A tree may be perfect in its first year of growth; but it does not attain its maturity. So with the Christian: he may be a true child of God, but not a matured Christian. The eighth of Romans is very important, and we should be very familiar with it. In the fourteenth verse the apostle says: “For as many as are led by the Spirit of God they are the sons of God.” Just as the soldier is led by his captain, the pupil by his teacher, or the traveller by his guide; so the Holy Spirit will be the guide of every true child of God.
Then let me call your attention to another fact. All Paul’s teaching in nearly every Epistle rings out the doctrine of assurance. He says in 2 Corinthians 5:1: “For we know that if our earthly house of this tabernacle were dissolved, we have a building of God, a house not made with hands, eternal in the heavens.” He had a title to the mansions above, and he says— I know it . He was not living in uncertainty. He said: “I have a desire to depart and be with Christ” (Philippians 1:23); and if he had been uncertain he would not have said that. Then in Colossians 3:4, he says: “When Christ, who is our life, shall appear, then shall ye also appear with Him in glory.” I am told that Dr. Watts’ tombstone bears this same passage of Scripture. There is no doubt there.