It’s called 2 Tim 2:15. Not exactly a secret, but completely ignored by those who want to believe they are spiritual Israel, or are bringing in the Kingdom, or have some sort of Apostolic Succession, or believe that water baptism saves, or teaching that faith plus works save. Sound familiar?
2 Timothy 2:15 is what the Catholic Church adheres to unlike your own sect, which only dates from the 17th century.
My response is from Matthew 7:15 “Beware of the false prophets, who come to you in sheep’s clothing, but inwardly are ravenous wolves.”
The following verses apply to Protestantism and the followers of your sect because you have not kept the traditions of the apostles and have created a new gospel.
Galatians 1:8 But though we, or an angel from heaven, preach a gospel to you besides that which we have preached to you, let him be anathema.
Acts 20:30 Even from your own number men will arise and distort the truth in order to draw away disciples after them.
2 Peter 3:16 He writes the same way in all his letters, speaking in them of these matters. His letters contain some things that are hard to understand, which ignorant and unstable people distort, as they do the other Scriptures, to their own destruction.
A sacrament is an outward sign of inward grace, and it is not a human work. To think otherwise is to depart from scripture as well as tradition.