paul is teaching christian to stay in contact with god, with spiritual gift, prayer, the bible, so when you have ran your life, you can have the same statement, i have kept the faith in a god through jesus.
then after paul dies, 70ad hapened. his teaching also provide , foundations that, prove faith in god. not faith in paul or peter or any man,
29 And if you are Christ's, then you are Abraham's offspring, heirs according to promise.
if we are hiers and sons , then the message must have the foundation to be correct, or you have nothing, etc