How Did The Father Testify For The Son?

There is no testimony weightier than that which comes from God himself. However, men may ask: "How sure are you that it is God testifying? How can you prove it?"
The truth is we know not by physically having God's signs or outwardly seeing evidences. We simply know it when we look at how His son, Jesus Christ, does and finish the work of God. When we look at the extent of the works accomplish, we affirm that it is never by human efforts but solely by the hands of God's grace and sovereignty.
God testifies for us by how we yield him into our lives, doing His works and manifesting His power through our circumstances and fields.
Our lives, His testimonies.