'Christianity refuses to be proved first & practiced afterwards: its practice & its proof go hand in hand,' wrote I. R. Illingworth.
The sermons of a certain preacher were magnificent, but his life was so inconsistent with his profession that, when he was in the pulpit, his congregation wished he would never leave it; and, when he was out of the pulpit, they wished he would never enter it again.
“But I discipline my body and keep it under control, lest after preaching to others I myself should be disqualified.” – Paul (1 Cor 9:27 ESV)
“A man's life is always more forcible than his speech. When men take stock of him they reckon his deeds as dollars and his words as pennies. If his life and doctrine disagree the mass of onlookers accept his practice and reject his preaching.” - Charles Spurgeon.