George Whitfield, a famous British preacher in the 18th Century, sailed across the Atlantic thirteen times (taking six weeks to three months), so he became as famous a preacher in the American colonies as he was on England. He preached to vast crowds without a PA system. He must must have had spectacular lungs and vocal cords. Again and again, he preached, he preached from John 3:3, “You must be born again”. Somebody eventually got really upset with him. He concerned him one day and asked, “Mr Whitefield, why is it you keep preaching again and again, ‘You must be born again’?” “Because, sir,” Whitefield replied, “you must be born again”.
(Source: The God Who Is There, D A Carson)