This expression is a wish for staying away from obstacles, barriers that one can meet while doing something. The "stumbling stone" is a suchlike expression. “Don’t be afraid of what they fear. Don’t let them frighten you! If you shall trust in Him, He shall be to you for a sanctuary; and you shall not come against [Him] as against a stumbling stone, neither as against the falling of a rock" (Isa 8:14-LXX).