John 8:32" And ye shall know the truth, and the truth shall make you free."
Some people often look for a loophole, look for a Catch 22 or look for any reason to disagree! Pray for this sort and preach the Gospel to those who truly want freedom, and if they need further assurance "USE WORDS"
Do what you know how to do, and God will anoint your works! To know how to build airplanes but you dedicate your life to painting houses is wasting your gift, OBEDIENCE to the word of God brings freedom and opens the door to eternal life, and that door swings both ways for you as well as others!
Do not forget you are working out your own salvation as well (IF) you truly know it live it. Your greatest witness is not so much what you say, or how well you say it, but instead how well you live it!