Joh 6:29 Jesus told them, “This is the only work God wants from you: Believe in the One He has sent.”
Do we add and detract from His Word, much like the Scribes and Pharisees? Work out your Salvation with fear and trembling means you are given it, now exercise it. Faith with out works is dead means there is still faith and salvation , but it is not being exercised, it is not growing.
Being P or RC is not the issue here. What is God’s positon, not what is the RC and P positon.
I have checked a number of Bible translations and only the New Living Translation has "This is the only work." "Only" is not to be found in any of the other translations. Indeed, the Greek is Τοῦτό ἐστιν τὸ ἔργον τοῦ θεοῦ ἵνα πιστεύητε εἰς ὃν ἀπέστειλεν ἐκεῖνος / "This is the work of God, that you should believe in Him whom He sent." So who is adding to the Word of God here? And if we are to believe in Jesus, then we must also believe in his instruction that we must keep the Commandments, not merely believe in the his salvific work.