I think you would find it to be non-essential for you to keep her any longer, but extremely essential that you should discharge her! And what shall we say of those men who put aside the words of Christ, and say, “His precepts are quite non-essential”? Why, I think because they are non-essential, they therefore become the test of your obedience! If you could be saved by them, and if they were necessary to your salvation, your selfishness would lead you to observe them; but inasmuch as they are not necessary to your salvation, they become tests of your willingness to obey Christ!
~ Charles Spurgeon, sermon #359:
There is no such thing as a non-essential biblical doctrine. All biblical doctrine is essential, else why would the King make dictates? Does God indeed say things that are not to be taken seriously? Does He waste His breath? Did He not say that even a jot and title will not be removed until the Law is accomplished? And did the Author of Scripture pick each word down to its particular verb tense to make His sovereign point?
Biblical Christians will not question nor have the audacity to change what the King has demanded. When HE states who is to be baptized and how its to be done, for example, this is not an option to be ignored or for us to change. We obey HIM as He has already spoken. Spurgeon is right: the test of faith is to see if one will indeed submit to the Lordship of the Lord...else why bother calling Him "Lord, lord" and not do what He says? Do we know better than the King of kings and Lord of lords? No we do not.
Mat 5:19 "Whoever then annuls one of the least of these commandments, and teaches others to do the same, shall be called least in the kingdom of heaven; but whoever keeps and teaches them, he shall be called great in the kingdom of heaven.
Mat 5:20 "For I say to you that unless your righteousness surpasses that of the scribes and Pharisees, you will not enter the kingdom of heaven.
Rom 16:26 But now is made manifest, and by the scriptures of the prophets, according to the commandment of the everlasting God, made known to all nations for the obedience of faith
Jas 1:19 Know this, my beloved brothers: let every person be quick to hear, slow to speak, slow to anger;
Eric Powers of The Biblical Christ Institute wrote something more about this false dichatomy between essential and non-essential truth, called "Doctrinal Triage".