God acknowledged Jesus as his son. We have the words of witnesses that, on two occasions, heard God speak with a voice that could be understood by people. This voice confirmed that Jesus was his son. On the second occasion, he also commanded that people should listen to Jesus.
The first of these occasions was Jesus’ baptism. (Matthew 3:13-17; Mark 1:9-11; Luke 3:21-22 )
The second occasion was on a mountain where Jesus was transfigured (Matthew 17:1-8; Mark 9:2-8; Luke 9:28-36.)
The apostle Peter was with Jesus on the mountain on this second occasion and confirmed that he and his companions heard God acknowledge Jesus as his son:
“For he received honor and glory from God the Father when that voice was conveyed to him by the Majestic Glory, saying, ‘This is my Son, my Beloved, with whom I am well pleased.’ We ourselves heard this voice come from heaven, while we were with him on the holy mountain.” (2 Peter 1:17-18)