For whatever is born of God overcomes the world; and this is the victory that has overcome the world—our faith. 1 John 5:4
The assurance that John speaks from is knowledge acquired first-hand. He has walked with the Lord, listened to His teaching, seen the miracles, and experienced the power. He has viewed His transfiguration, death, burial and resurrection. He has seen Him going into heaven, and experienced the coming of the Holy Spirit.
John does not want us settling for less, missing eternal life. So here, he rehearses “the basics” that we cannot ignore or rewrite. This will be our guide, to discern true and false teachers as well.
Jesus, the Son of God, has come in the flesh. He is, was, and always has been God. He has paid for our sin debt through His very real death on the cross. New life is offered to us, as we believe the truth of the Gospel and put our faith/trust in Him alone.
New life here and now is a life of faith. This faith-walk helps us to overcome the obstacles that the enemy challenges us with, in this fallen world. Overcomers have victory by reliance on Christ; not on our own merits, strengths or efforts.
Thankfully, His commands are far from awful, unbearable, harsh or joyless. Instead, a life of faith demonstrated by keeping His commands actually protects us and leads us to the greatest joy—that of knowing Him and being pleasing to Him. This is not “happiness” that comes only when circumstances are “good,” but peace in assurance that regardless of the test, pain, or loss, all is well for those who have forever been saved and set free by the finished work of Christ.
One day, faith will rest, being forever exchanged for sight.