"God so loved the world that He gave His Only-begotten Son, that whosoever believes in Him should not perish, but have everlasting life." (John 3:16)
What He says, is this: Marvel not that I am to be lifted up that you may be saved, for this seems good to the Father, and He has so loved you as to give His Son for slaves, and ungrateful slaves. Yet a man would not do this even for a friend, nor readily even for a righteous man; as Paul has declared when he said, “scarcely for a righteous man will one die.” Here Christ speaks concisely for each word had much significance. For by the expression, so loved, and that other, God the world, He shows the great strength of His love. Large and infinite was the interval between the two. He, the immortal, who is without beginning, the Infinite Majesty. They who are but dust and ashes, full of ten thousand sins, ungrateful, and have at all times offended Him. These are the ones He loved. Again, the words which He added after these are alike significant, when He says, that He gave His Only-begotten Son. Not a servant, not an Angel, not an Archangel. And yet no one would show such anxiety for his own child, as God did for His ungrateful servants.
His Passion He sets before him not very openly, but rather darkly. But the advantage of the Passion He adds in a clearer manner, saying; That every one that believes in Him. should not perish, but have everlasting life. For when He had said, must be lifted up, He alluded to death. But lest the hearer should be made downcast by these words, forming some mere human opinions concerning Him, and supposing that His death was a ceasing to be, observe how He sets this right, by saying, that He who was given was The Son of God, and the cause of life, of everlasting life. He who procured life for others by death, would not Himself be continually in death. For if they who believed on the Crucified perish not, much less does He perish who is crucified. He who takes away the destitution of others much more is He free from it. He who gives life to others, much more to Himself does He flow forth life. Do you see that everywhere there is need of faith? The Cross is the fountain of life; which reason cannot easily allow. But faith which goes beyond the weakness of reasoning. So from where did God so love the world? From no other source, only from his goodness.