30 Jesus replied and said: “This voice came not to help Me (because of Me), but to help you (because of you).
31 Now is the judgement of this world; now the ruler of this world will be thrown outside.
Those who are used to public speaking may from time to time say things that are for the benefit of some of their hearers, but that are not helpful for others. A politician will say things that inspire members of their own party, or floating voters. At other times they may say something that is designed to antagonise members of different parties.
When God speaks to us it is always for our benefit.
The Bible is full of occasions when God spoke to His people. We know that He spoke to Adam and Eve in the Garden of Eden.
He spoke to Noah and instructed him to build the ark, and gave him the details of the ark.
God spoke to Abraham and told him to leave his father’s house and go to a place He would show him.
These are just a few of the many occasions when God spoke to His people. However, people in the days of the New Testament were not used to hearing the voice of God. They never expected to hear Him. This is why they were uncertain as to what they heard: was it thunder, or was it the voice of an angel?
Jesus confirms that it was a voice, and perhaps we can assume that the inference is that it was the voice of the Father, since Jesus had been praying to Him.
Since Jesus told the people that the voice of God they heard was for their benefit, we must ask what was that benefit.
Jesus had been telling the people that He was the Son of the Father; He had been telling them that He and the Father are one; He had been telling them that He could do nothing on His own. The voice that they heard was to confirm to them that all Jesus had said was true. The benefit of them hearing the voice of the Father was a verification of the truth of who Jesus is.
God cannot and will not deny Himself, and He will always confirm to us that Jesus is the Way, the Truth and the Life and that no one comes to the Father except through Him (John 14.6).