The quotations below from the Apostolic Constitutions (375 AD) give historical perspective on the attitude of Christians regarding martyrdom and the eternal importance of never denying Jesus. As you can read below, it was taught that those Christians that were unfaithful to their confession risked losing their salvation. The memories of persecution were still relatively fresh for the church at this point, which makes these quotes all the more impactful.
I’ve made the particularly relevant portions below bold, although it’s all worth the read.
But he that denies himself to be a Christian, that he may not be hated of men, and so loves his own life more than he does the Lord, in whose hand his breath is, is wretched and miserable, as being detestable and abominable, who desires to be the friend of men, but is the enemy of God, having no longer his portion with the saints, but with those that are accursed; choosing instead of the kingdom of the blessed, that eternal fire which is prepared for the devil and his angels: not being any longer hated by men, but rejected by God, and cast out from His presence.
For of such a one our Lord declared, saying: “Whosoever shall deny me before men, and shall be ashamed of my name, I also will deny and be ashamed of him before my Father which is in heaven.” And again He speaks thus to us ourselves, His disciples: “He that loveth father or mother more than me, is not worthy of me; and he that loveth son or daughter more than me, is not worthy of me; and he that taketh not his cross, and followeth after me, is not worthy of me. He that findeth his life, shall lose it; and he that loseth his life for my sake, shall find it. For what is a man profited, if he shall gain the whole world, and lose his own soul? or what shall a man give in exchange for his soul?” And afterwards: “Fear not them that kill the body, but are not able to kill the soul; but rather fear Him who is able to destroy both soul and body in hell.” (5.1.4)
And a little later:
Let us therefore renounce our parents, and kinsmen, and friends, and wife, and children, and possessions, and all the enjoyments of life, when any of these things become an impediment to piety. For we ought to pray that we may not enter into temptation; but if we be called to martyrdom, with constancy to confess His precious name, and if on this account we be punished, let us rejoice, as hastening to immortality. When we are persecuted, let us not think it strange; let us not love the present world, nor the praises which come from men, nor the glory and honour of rulers, according as some of the Jews wondered at the mighty works of our Lord, yet did not believe on Him, for fear of the high priests and the rest of the rulers: “For they loved the praise of men more than the praise of God.”
But now, by confessing a good confession, we not only save ourselves, but we confirm those who are newly illuminated, and strengthen the faith of the catechumens. But if we remit any part of our confession, and deny godliness by the faintness of our persuasion, and the fear of a very short punishment, we not only deprive ourselves of everlasting glory, but we shall also become the causes of the perdition of others; and shall suffer double punishment, as affording suspicion, by our denial that that truth which we gloried in so much before is an erroneous doctrine.
Wherefore neither let us be rash and hasty to thrust ourselves into dangers, for the Lord says: “Pray that ye fall not into temptation: the spirit indeed is willing, but the flesh is weak.” Nor let us, when we do fall into dangers, be fearful or ashamed of our profession. Nor let us, when we do fall into dangers, be fearful or ashamed of our profession. For if a person, by the denial of his own hope, which is Jesus the Son of God, should be delivered from a temporary death, and the next day should fall dangerously sick upon his bed, with a distemper in his bowels, his stomach, or his head, or any of the incurable diseases, as a consumption, or gangrene, or looseness, or iliac passion, or dropsy, or colic, and has a sudden catastrophe, and departs this life; is not he deprived of the things present, and loses those eternal? Or rather, he is within the verge of eternal punishment, “and goes into outer darkness, where is weeping and gnashing of teeth.” (5.1.6)
The quotes speak for themselves. Let’s not deny Christ, fearing the temporary, and thus lose the eternal.
If you want to read more from the Apostolic Constitutions, check out my post on the early church teaching that continued obedience after baptism is necessary for salvation.