Treasury of Scripture Knowledge
John gave testimony about Jesus, shouting out, "This person is the one about whom I said, 'He who will come after me ranks above me because He existed before me.'"
The one who has the bride is the groom; but the best man, who stands up with him and listens to him [take his vows], is very happy when he hears him speak. So, [now] my joy is complete [i.e. over hearing about Jesus' ministry].
So, Peter testified and urged the crowd with many additional words, saying, "Save yourselves from [the condemnation coming on] this sinful generation [by responding to this message]."