I have great heaviness and continual sorrow in my heart. – Romans 9:2

Our concern for souls must be worked in us by the Holy Spirit. It must come irresistibly upon us and become a master passion. Just as the birds, when the eggs are in the nest, have upon them a natural feeling that they must sit on those eggs and that they must feed those little fledglings which will come from the eggs—so if God calls you to win souls, you will have a natural love for them, a longing worked in you by the Holy Spirit so that the whole of your being will run out in that direction, seeking the salvation of men. The Apostle goes on to say that he had great heaviness—not only heaviness, but great heaviness. Was he, therefore, an unhappy man? By no means! He had great joy in other things, though he had great heaviness on this point…Whenever Paul’s thoughts turned towards his Jewish brethren, a great heaviness came upon him. It bore him down and he would have sunk under it if it had not been for sustaining grace. “O God,” he said, “shall my nation perish? Shall my people die? Shall my kinsmen be anathema? Shall it come to this, that they shall hear the Gospel in vain and perish, after all?” …He thought of his brethren and their unbelief—and then he thought of how they had been the enemies of Christ and, therefore, sorrow filled his heart. I could wish that in full many a professor the same sorrow reigned, for then there would be much more holy work done for souls! …Let other men’s sins grieve you! Let their eternal destiny be often on your mind! No better spur can be needed. You will labor for their good in proportion as you feel for them. I do not think that I can ask a better thing for the unconverted than that the converted may be in heaviness over them! ~ C.H. Spurgeon

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