He that hath the Son hath life… – 1 John 5:12

Having the Son is not only the source of life, but the result of life. When the great doors were opened of the Black Hole in Calcutta, and the pure air went streaming in, there were many lungs which did not receive that air, for the simple reason that the most of those who had been so barbarously confined were dead, and to them the fresh oxygen had come too late; but there were a few which gladly and at once received the breath of heaven, and such as were still alive walked forth from amidst the corpses into the open air. Now, when a man receives Jesus into his soul as life from the dead, his faith is the sure indicator of a spiritual and mysterious life within him, in the power of which he is able to receive the Lord. Jesus is freely preached to you, His grace is free as the air, but the dead do not breathe that air-those who breathe it are, beyond all doubt, alive. Christ is presented to you in the preaching of the gospel as freely as the water from the drinking fountain at the corner of the street; but the dead man drinketh not, his lips care not for the flowing crystal; he who drinks is evidently alive. The reception of Jesus Christ is the sure result of a heavenly life palpitating within the soul Thus you see the evidence is good, from several points of the compass; looking at the soul’s business from several ways, faith still becomes with equal clearness a witness that the man who has it possesses the divine life within him.  “I do not know,” says one, “when I was converted.” My dear friend, have you the Son of God? Do you trust in Jesus Christ? That is quite enough. If thou canst from the heart say, “I trust Jesus Christ,” though thou hast no spiritual biography worth recording, thou hast life. ~ C.H. Spurgeon

https://www.blueletterbible.org/Comm/spurgeon_charles/sermons/0755.cfm