The relation of experience is the most convincing preaching. A little girl of eight years came from her chamber to her mother, radiant with joy, and said, "Mother, God has pardoned my sins and given me a new heart; may I run across the street and tell the old cobbler?" "It will do no good, my child, for he is a confirmed and outspoken infidel," said the mother. "But it will do me good to tell him, and it may do him good, too; may I not go?" "Yes, if your heart is so much set on it." She went and told in artless simplicity of her sense of sin and guilt, of her repentant tears and prayers, of her trust in Jesus Christ who died to become her Saviour, of the light and joy which sprang up in her heart, of the feeling of love towards God, and of a voice sounding within saying, "Father, Father;" and whenever she thought of God he seemed no more like a policeman to arrest her, but a person more loving and tender than her mother. Before she finished her account of her joyful conversion her solitary hearer was in tears, which did not cease to flow until they were wiped away by the hand of divine mercy writing forgiveness on his believing heart.
When Paul rose to the summit of his eloquence, whether as a prisoner before Felix or Festus, or addressing the riotous Hebrews in their temple, he presented no elaborate chain of reasoning, but narrated in unadorned style his own experience of the transforming power which arrested him and, when he was obedient to the heavenly vision, made a new man of him when he had still in his pocket a commission to arrest and handcuff and drag to Jerusalem all the Hebrew disciples of Jesus found in Damascus.
Testifying of personal conscious salvation through faith is a kind of effective preaching to which all believers are called.
— edited from Jesus Exultant (1899) Chapter 5.