This is he of whom I said, ‘After me comes a man who ranks before me, because he was before me.’ (John 1:30, ESV)
John the Baptist elaborates on this Lamb of God. He is the one whom he had been saying would come. It was important to John that, even though he was the herald... the predecessor... John wanted all to know that the Christ was pre-existent. Before John was... He was.