The stumblingblock of the Christian is causing others to stumble.
Isaiah 57:13-15 When thou criest, let thy companies deliver thee; but the wind shall carry them all away; vanity shall take them: but he that putteth his trust in me shall possess the land, and shall inherit my holy mountain; (14) And shall say, Cast ye up, cast ye up, prepare the way, take up the stumblingblock…