In this was manifested the love of God toward us, because that God sent his only begotten Son into the world, that we might live through him. In this was manifested the love of God - The mission of Jesus Christ was the fullest proof that God could give, or that man could receive, of his infinite love to the world.
That we might live through him - The whole world was sentenced to death because of sin; and every individual was dead in trespasses and sins; and Jesus came to die in the stead of the world, and to quicken every believer, that all might live to him who died for them and rose again. This is another strong allusion to John 3:16 : God so loved the world, that he gave his only-begotten Son, that whosoever believeth in him should not perish, but have everlasting life; where the reader is requested to see the note on John 3:16.