'Be Careful' in the Bible

Like an expert builder, I laid a foundation, as God commissioned me to do, and now someone else is building upon it. But let everyone be careful how he does so.

Be careful that no one fails to gain God's favor, or some poisonous root may come up to trouble and contaminate you all??16 some immoral or godless person like Esau, who sold his very birthright for one single meal.