Sometimes, saying something makes it so. If you have that kind of power, you can use a middle perfect to great effect.

καὶ εἶπεν Τωβιας Οὐ μὴ φάγω ἐντεῦθεν οὐδὲ μὴ πίω, ἕως ἂν διαστήσῃς τὰ πρὸς ἐμέ. καὶ εἶπεν αὐτῷ Ραγουηλ ὅτι Ποιῶ, καὶ αὐτὴ δίδοταί σοι κατὰ τὴν κρίσιν τῆς βίβλου Μωυσέως, καὶ ἐκ τοῦ οὐρανοῦ κέκριταί σοι δοθῆναι, κομίζου τὴν ἀδελφήν σου. ἀπὸ τοῦ νῦν σὺ ἀδελφὸς εἶ αὐτῆς καὶ αὐτὴ ἀδελφή σου, δέδοταί σοι ἀπὸ τῆς σήμερον καὶ εἰς τὸν αἰῶνα, καὶ ὁ κύριος τοῦ οὐρανοῦ εὐοδώσει ὑμᾶς, παιδίον, τὴν νύκτα ταύτην καὶ ποιήσαι ἐφ̓ ὑμᾶς ἔλεος καὶ εἰρήνην. καὶ ἐκάλεσεν Ραγουηλ Σαρραν τὴν θυγατέρα αὐτοῦ, καὶ ἦλθεν πρὸς αὐτόν, καὶ λαβόμενος τῆς χειρὸς αὐτῆς παρέδωκεν αὐτὴν αὐτῷ καὶ εἶπεν Κόμισαι κατὰ τὸν νόμον καὶ κατὰ τὴν κρίσιν τὴν γεγραμμένην ἐν τῇ βίβλῳ Μωυσέως δοῦναί σοι τὴν γυναῖκα, ἔχε καὶ ἄπαγε πρὸς τὸν πατέρα σου ὑγιαίνων, καὶ ὁ θεὸς τοῦ οὐρανοῦ εὐοδώσαι ὑμῖν εἰρήνην.
But Tobias said, “I will neither eat nor drink anything until you settle the things that pertain to me.” So Raguel said, “I will do so. She is given to you in accordance with the decree in the book of Moses, and it has been decreed from heaven that she be given to you. Take your kinswoman; from now on you are her brother and she is your sister. She is given to you from today and forever. May the Lord of heaven, my child, guide and prosper you both this night and grant you mercy and peace.” 12 Then Raguel summoned his daughter Sarah. When she came to him he took her by the hand and gave her to Tobias, saying, “Take her to be your wife in accordance with the law and decree written in the book of Moses. Take her and bring her safely to your father. And may the God of heaven prosper your journey with his peace.”
Tobit 7:12–13 (Alternate Text) = Tobit 7:11-12 (NRSV)