We can only do what God says. To suggest something else is not faith. Paul said to the Romans, “and whatever is not of faith is sin” (Rom. 14:23). A Biblical command or approved example is easy to do in faith. From the pulpit I can encourage Christians to participate in the Lord’s Supper. I am very confident, it is a matter of faith. But I could not in good faith tell the Christians that God is happy if we include in the communion a roasted lamb. To say that would be winging it, to be presumptuous and not faith.
When God speaks, people of faith listen to Him. God means what He says and Christian know it is presumptuous to think otherwise. If God says Jesus is the only way to heaven, He is not saying that there are many acceptable religious options. When God says we must worship Him in spirit and truth, He is not saying do what makes you feel good. When God is specific, His words exclude other options. When Jesus says to be immersed into the Father, Son, and Holy Spirit, He is not merely saying to “get wet”.
Doing the will of God means doing what He says. When someone in authority tells you to “run, don’t walk”, do you walk? If a judge says you must not drink, do you think “stay under the ‘legal’ limit”? When a teacher says “20 page report”, do you think 10 is acceptable? God is not like an equal that we can barter or argue with the terms of our relationship. He is the Almighty and the question is do we trust Him or not? If we trust in Him, then we do what He says. His specific words necessarily exclude everything else. Doing what “feels good” to us doesn’t come to the attitude of faith we must have.