The Gemara (in Kesubos 63a) says, “When Rabbi Akiva returned, he brought twelve thousand students with him. As he approached his home, he heard a certain old man saying to [his wife], ‘Until when will you lead a life of living widowhood?’ She answered him, ‘If he would listen to me, he would sit in the beis medrash another twelve years.’ Hearing this, [R’ Akiva] said to himself, ‘I am acting with my wife’s permission.’ He went back and sat another twelve years in the beis medrash…”
Who was the old man that was talking to Rabbi Akiva's wife?