Revelation 3:11

I have said all this about those who have been predestined to the kingdom of God, whose number is so fixed that not one can be added to it or taken from it. I have not been speaking of those who, although he had declared and spoken, have been called but not chosen, because they were not called according to his purpose. The fact that the number of the elect is fixed, not to be increased or diminished, is suggested even by John the Baptist, where he says, "Bring forth therefore fruit befitting repentance. And do not think to say to yourselves, 'We have Abraham for our father.' For I say to you that God is able out of these stones to raise up children to Abraham." The words show that those who do not bring forth fruit are to be cut off, in such a way, however, that the number [of children] promised to Abraham will not fall short. However, it is more openly declared in the Apocalypse: "Hold fast what you have, that no one receive your crown." For if another is not to receive a crown, unless someone first lose it, the number is fixed.

It is the wholesome precept of our Lord and Master: "He that endureth," saith He, "unto the end, the same shall be saved; " and again, "If ye continue," saith He, "in my word, ye shall be truly my disciples; and ye shall know the truth, and the truth shall make you free." We must endure and persevere, beloved brethren, in order that, being admitted to the hope of truth and liberty, we may attain to the truth and liberty itself; for that very fact that we are Christians is the substance of faith and hope. But that hope and faith may attain to their result, there is need of patience. For we are not following after present glory, but future, according to what Paul the apostle also warns us, and says, "We are saved by hope; but hope that is seen is not hope: for what a man seeth, why doth he hope for? But if we hope for that which we see not, then do we by patience wait for it." Therefore, waiting and patience are needful, that we may fulfil that which we have begun to be, and may receive that which we believe and hope for, according to God's own showing. Moreover, in another place, the same apostle instructs the righteous and the doers of good works, and them who lay up for themselves treasures in heaven with the increase of the divine usury, that they also should be patient; and teaches them, saying, "Therefore, while we have time, let us labour in that which is good unto all men, but especially to them who are of the household of faith. […]

That we must press on and persevere in faith and virtue, and in completion of heavenly and spiritual grace, that we may attain to the palm and the crown. In the book of Chronicles: "The Lord is with you so long as ye also are with Him; but if ye forsake Him, He will forsake you." In Ezekiel also: "The righteousness of the righteous shall not deliver him in what day soever he may transgress." Moreover, in the Gospel the Lord speaks, and says: "He that shall endure to the end, the same shall be saved." And again: "If ye shall abide in my word, ye shall be my disciples indeed; and ye shall know the truth, and the truth shall make you free." Moreover, forewarning us that we ought always to be ready, and to stand firmly equipped and armed, He adds, and says: "Let your loins be girded about, and your lamps burning, and ye yourselves like unto men that wait for their lord when he shall return from the wedding, that when he cometh and knocketh they may open unto him. Blessed are those servants whom their lord, when he cometh, shall find watching." Also the blessed Apostle Paul, that our faith may advance and grow, and attain to the highest point, exhorts us, saying: "Know ye not, that they which run in a race run all indeed, yet one receiveth the prize? So run, that ye may obtain. And they, indeed, that they may receive a corruptible crown; but ye an incorruptible." And again: "No man that warreth for God binds himself to anxieties of this world, that he may be able to please Him to whom he hath approved himself. […]

I am coming quickly, he says, having taken hold of you. Hold fast what you have, that no one may take your crown. And what do you hold fast? The genuine love toward the Lord, evidently, in which, having persevered until the end, you will …

I come quickly: hold fast that which thou hast. The Lord says he will come quickly, so that no one should give up in the struggle. For everything that passes happens quickly. What he tells him to hold fast is the conduct of heavenly life, …