We must preach to ourselves, before we preach to others; knowing that as teachers we are subject to a stricter judgment (James 3:1) from the One who looks not on the outward appearance, but at the heart (1 Sam. 16:7).
For since, in the wisdom of God, the world through wisdom did not know God, it pleased God through the foolishness of the message preached to save those who believe.
1 Corinthians 1:21
For we do not preach ourselves, but Christ Jesus the Lord, and ourselves your bondservants for Jesus' sake. For it is the God who commanded light to shine out of darkness, who has shone in our hearts to give the light of the knowledge of the glory of God in the face of Jesus Christ. But we have this treasure in earthen vessels, that the excellence of the power may be of God and not of us.
2 Corinthians 4:5-7