Presumption is doing something that you know is wrong, and yet we still expect that God will approve of it. For example, Cain’s wrongful offering to God. God has given no man liberty to depart from His requirements.
When Apostle Paul’s ship was wrecked on the Island of Melita, Paul was helping to start a fire when a viper came out of a bundle of sticks and bit Paul’s hand. He suffered no harm because He believed in God’s promise of protection from snakes.
God does not want us to take the viper to our bosom and expect Him to put a spell upon it so that it will not poison you with its venomous bite. Will you drink poison expecting God to provide an antidote? What the preacher did in his ignorance or presumption cost him His life (Mark 16:17-18). Be sure what you are doing is correct.