'Certain Man' in the Bible

What do you think? If {a certain man has} a hundred sheep, and one of them wanders away, will he not leave the ninety-nine on the hills and go [and] look for the one that wandered away?

And he said, "Go into the city to a certain man and tell him, 'The Teacher says, "My time is near. I am celebrating the Passover with you with my disciples." '