“I say the truth in Christ, I lie not, my conscience also bearing me witness in the Holy Spirit, that I have great heaviness and continual sorrow in my heart. For I could wish that I were accursed from Christ for my brethren, my kinsman according to the flesh, who are Israelites, to whom pertains 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 forever. Amen.”- Romans 9:1-5

What an intense man Paul was! Once convince him and his whole nature moved in the direction which he judged to be right. He was whole-hearted when he persecuted the Church of God and he was equally whole-hearted when, afterwards, he labored with all his might to build up the Church which he had sought to destroy! What a change was worked in Saul of Tarsus, that he who was so ardent a persecutor should become so fervent a preacher! His conversion is one of the proofs of the Divinity of Christianity. When you remember what he was by nature, you will marvel at the extraordinary change of thought and feeling which was worked in him! He who was cruel to the saints, who gave his voice against Stephen and held the garments of those that stoned him, became tenderhearted as a nurse towards her child! Though his Jewish brethren terribly persecuted him and pursued him from city to city, there is not a trace of resentment in any word he writes! Rather, he is full of gentleness. The lion had become a lamb and he that breathed out threats breathed out prayers! He who seemed to burn with enmity became a flame of love! I would to God we were all as thorough-going in the service of our Lord! The pity is that so many professing Christians appear to have no heart, while others borrow a heart for some occasions but do not seem to keep one permanently beating in their own bosoms. O for a warm, engine-like heart all consecrated and forever pulsing mightily! ~ C.H. Spurgeon

https://www.blueletterbible.org/comm/spurgeon_charles/sermons/1425.cfm