Original: Idamante approaches him, but because the two have not seen each other for a long time, recognition is difficult. When Idomeneo finally realizes the youth he must sacrifice for the sake of his vow is his own child, he orders Idamante never to seek him out again.
Simplified: When Idomeneo finally realizes it is his own son he must kill, he tells Idamante to go away and never see him again.