John 12:28 (ESV) … “Father, glorify your name.” Then a voice came from heaven: “I have glorified it, and I will glorify it again.”
The Lord burst suddenly into prayer—not a prayer that he might be kept from the hour, but that his Father might be glorified. “Father, glorify thy name. Then came a voice from heaven, saying, I have both glorified it, and will glorify it again. The people therefore, that stood by, and heard it, said that it thundered: others said, An angel spake to him. Jesus answered and said, This voice came not because of me, but for your sakes.”
This is the third time God had now spoken audibly from heaven. The first time was at his baptism, at the commencement of his ministry (Matthew 3:17); the second time was on the mount of transfiguration, at the climax of his ministry (Matthew 17:5); the third time is here, at the crisis of his ministry. The first time was when he went down into the waters of Jordan; the second time was when he was about to come down from the mount; the third time was when he prepared himself to go down into death.
The people standing around heard something loud but they were mystified as to how to explain it. Some thought it was a natural phenomenon, a thunderclap. Others thought it was a supernatural phenomenon, the voice of an angel. Neither group was able to discern what was said. The Lord instantly recognized his Father’s voice. He explained to the crowds that it was indeed a voice. But he himself did not need audible confirmation that he was in the Father’s will.
Evidently the disciples themselves either understood what was said to Jesus in this pronouncement, or else he told them. In it, God declared that he had already glorified his name in the ministry of Jesus and he would glorify it again.
From the context we deduce that the Father’s name had been glorified in the wilderness by the Lord’s victory over Satan and would be glorified again by the victory over Satan at Calvary and in the apocalypse. Satan is the one great moral blot in the universe. His character, career, and crimes constitute an abiding insult to the holiness and goodness of God. The Lord’s victories over Satan bring glory to God.
 Phillips, J. (2009). Exploring the Gospel of John: An Expository Commentary (Jn 12:28–30). Kregel Publications; WORDsearch Corp.