He that shall persevere We are here told, that to be saved it is not sufficient that we were once virtuous, we must persevere to the end. We are also assured of the same truth in Ezechiel. If the just man shall turn away from his justice, and shall commit iniquity, he shall die in his sins, and his justice which he hath done shall not be remembered. (Chap. iii, ver. 20.) (Haydock)
Some, says St. Chrysostom, are accustomed to be fervent at the beginning of their conversion, but afterwards grow remiss; of what advantage are seeds that flourish in the beginning, but afterwards wither and die? (St. Chrysostom in St. Thomas Aquinas)
Ap. Anselm: Having placed the comfort first, He adds the more alarming perils; "Brother shall deliver up brother to death, and the father the son; children shall rise against parents, to put them to death.”
Hom. in Ev., xxxv, 3: Wrongs which we suffer from strangers, pain us less than those we suffer from men on whose affections we had counted; for besides the bodily affliction, there is then the pain of lost affection.
And these things in another point of view likewise were sufficient to rouse up their spirits; since at any rate the power of their gospel was to blaze up so high, as that nature should be despised, and kindred rejected, and the Word preferred to all, chasing all mightily away. For if no tyranny of nature is strong enough to withstand your sayings, but it is dissolved and trodden under foot, what else shall be able to get the better of you? Not, however, that your life will be in security, because these things shall be; but rather ye will have for your common enemies and foes them that dwell in the whole world.
5. Where now is Plato? Where Pythagoras? Where the long chain of the Stoics? For the first, after having enjoyed great honor, was so practically refuted, as even to be sold out of the country, and to succeed in none of his objects, no, not go much as in respect of one tyrant: yea, he betrayed his disciples, and ended his life miserably. And the Cynics, mere pollutions as they ...
The courts of justice will go against you. Kings will assail you, as will governors, the synagogues of the Jews and the magistrates of the Gentiles. Both rulers and ruled will combat you. He was preparing them not only for what was to befall them in Palestine but also throughout the world. For they were soon to be sent to the Gentiles with this same proclamation. In doing so they would find that the whole world opposes them. In this spiritual warfare all that dwell upon the earth, all peoples, tyrants and kings, will be arrayed against them. The Gospel of Matthew, Homily
What follows is yet more dreadful, “Ye shall be hated of all men;” they sought to exterminate them as common enemies of all the world. To this again is added the consolation, “For my name’s sake;” and yet further to cheer them, "Whosoever shall endure to the end, he shall be saved.” For many are hot and zealous in the beginning, but afterwards grow cool, for these, He says, I look at the end. For where is the profit of seeds that only sprout at first? Wherefore He requires a sufficient endurance from them.
But that no man should say, that Christ wrought all things in His Apostles, and therefore it is nothing wonderful that they were made such as they were, since they did not bear the burden of these things, therefore He says, that perseverance was their work. For though they were rescued from their first perils, they are preserved for still harder trials, which again shall be followed by others, and they shall be in danger of snares as long as they live. This He covertly intimates when...
And the reward is not for those that begin, but for those that bring to an end.
That is, He who shall not let go the commands of the faith, nor fall away in persecution, shall be saved; he shall receive the reward of the heavenly kingdom for his earthly persecutions. And note that ‘the end’ does not always mean destruction, but sometimes perfection, as in that, “Christ is the end of the Law.” So the sense here may be, “Whosoever shall endure to the end,” that is, in Christ.
"Hated by all men" means "hated by many." For not everyone hated them, as there were those who accepted the faith. It is he who patiently endures until the end, and not only in the beginning, who will partake in eternal life.