Circumcision

בראשית מה ,יב: וְהִנֵה עֵינֵיכֶם רֹאוֹת

The Baal HaTurim comments that the Gematria of עיניכם ראות (with the principal of אם הכלל) equals the Gematria (807) of the phrase הראיתי לכם המילה (I have shown you the circumcision).

When Yosef revealed his identity to his brothers, they were hesitant to accept his words. Although he revealed many details of their personal life that a stranger would not know, they still did not believe him. He spoke to them in Lashon haKodesh, yet they remained doubtful. Finally, Yosef showed them that he was circumcised and then they believed him. Of course, this needs to be understood since Yosef had already circumcised all the Egyptians.