I say the truth in Christ, I lie not, my conscience also
bearing me witness in the Holy Ghost, That I have great
heaviness and continual sorrow in my heart. For I could
wish that myself were accursed from Christ for my brethren, my kinsmen
according to the flesh: Who are Israelites; to whom
pertaineth the adoption, and the glory, and the covenants, and the
giving of the law, and the service of God, and the promises;
Whose are the fathers, and of whom as concerning the flesh Christ came,
who is over all, God blessed for ever. Amen.
St. John Chrysostom said in On the Priesthood, Book 3…
"No man loved Christ more than Paul: no man exhibited greater zeal, no man was counted worthy of more grace: nevertheless, after all these great advantages, he still has fears and tremblings concerning this government and those who were governed by him. 'I fear,' he says, 'lest by any means, as the serpent beguiled Eve through his subtlety, so your minds should be corrupted from the simplicity which is in Christ.' (II Cor.11:3) And again, 'I was with you in fear and in much trembling;' (I Cor.2:3) and this was a man who had been caught up to the third Heaven, and made partaker of the unspeakable mysteries of God, (II Cor.12:4) and had endured as many deaths as he had lived days after he became a believer – a man, moreover, who would not use the authority given him from Christ lest any of his converts should be offended. If, then, he who went beyond the ordinances of God, and nowhere sought his own advantage, but that of those whom he governed, was always so full of fear when he considered the greatness of his government, what shall our condition be who in many ways seek our own, who not only fail to go beyond the commandments of Christ, but for the most part transgress them" 'Who is weak,' he says, 'and I am not weak? Who is offended and I burn not?' (II Cor.11:29) Such a one ought the priest to be, or, rather, not such only: for these are small things, and as nothing compared with what I am about to say."
"And what is this? 'I could wish,' he says, 'that myself were accursed from Christ for my brethren, my kinsmen according to the flesh.' (Rom.9:3) If any one can utter such a speech, if anyone has the soul which attains to such a prayer, he might justly be blamed if he took to flight: but if any one should lack such excellence as much as I do, he would deserve to be hated, not if he avoided the office, but if he accepted it."
Augustine in The City of God, Book XIV wrote:
"…the citizens of the holy city of God, who love according to God in the pilgrimage of this life, both fear and desire, and grieve and rejoice…all these affections of theirs are right…grieve for sin…rejoice in good works…according as they are strong or weak, they fear or desire to be tempted, grieve or rejoice in temptation…not only on their own account do they experience these emotions, but also on account of those whose deliverance they desire and whose perdition they fear, and whose loss of salvation affects them with grief or with joy…that hero, I say, and athlete of Christ, instructed by Him, anointed of His Spirit, crucified with Him, glorious in Him, lawfully maintaining a great conflict on the theatre of this world, and being made a spectacle to angels and men (I Cor.4:9) and pressing onwards for the prize of his high calling, (Phil.3:14) – very joyfully do we with the eyes of faith behold him rejoicing with them that rejoice, and weeping with them that weep; (Rom.12:15) though hampered by fightings without and fears within; (II Cor7:5) desiring to depart and to be with Christ; (Phil.1:23) longing to see the Romans, that he might have some fruit among them as among other Gentiles; (Rom.1:11-13) being jealous over the Corinthians, and fearing in that jealousy lest their minds should be corrupted from the chastity that is in Christ; (II Cor.11:1-3) having great heaviness and continual sorrow of heart for the Israelites, (Rom.9:2) because they, being ignorant of God's righteousness, and going about to establish their own righteousness, have not submitted themselves unto the righteousness of God; (Rom.10:3)…"