A.B. Simpson emphasizes the importance of spiritual maturity in his sermon 'Grow Up Into Him in All Things,' comparing the ripening of fruit to the development of a Christian's character. He notes that while many Christians possess good qualities, they often remain unrefined and sour due to life's challenges and personal struggles. Simpson encourages believers to allow God to work within them to cultivate sweetness and maturity, rather than relying solely on their efforts. He highlights that true growth comes from a deep relationship with God, which transforms their lives and brings joy. Ultimately, the sermon calls for Christians to seek inner growth and ripeness in their faith.

Harvest is a time of ripeness. Then the fruit and grain are fully developed, both in size and weight. Time has tempered the acid of the green fruit. It has been mellowed and softened by the rains and the heat of summer. The sun has tinted it into rich colors, and at last it is ready and ripe to fall into the hand. So the Christian life ought to be. There are many things in life that need to be mellowed and ripened. Many Christians have orchards full of fruit, but the fruit is green and sharp to the taste. There is a great deal in these Christians that is good, but it is incomplete-very sharp and sour. Perhaps something goes wrong in their domestic lives. They become flustered and cross and lose their confidence in God, and then, of course, their Christian joy. These things produce regret and all kinds of misery. Every day there are things for which we are sorry. We know we are not ripe and mellow and that we cannot become so by trying. We cannot bring the sweetness in. It must be wrought out from within.