For the first part of the verse, compare 4.12-13. Tobias must now be wondering who his companion is, since Raphael was not present when Tobit gave Tobias advice about who to marry.
Do you not remember your father’s orders…?: This rhetorical question has the force of a strong statement; for example, it may be rendered “You have already forgotten what your father instructed you. He told you to marry a woman from your own tribe, didn’t he?” As in the example, Good News Translation divides this long question into two shorter sentences; many translators will find this restructuring helpful.
A wife from your father’s house; that is, “from your own tribe” (Good News Translation), or even “from his [the father’s] side of the family” (Contemporary English Version).
Now listen to me, brother: “Carefully” in “listen carefully” (Good News Translation) represents nothing in the Greek text, but will be a natural expression of emphasis in many languages. Other possibilities are “Pay close attention to what I am saying” or simply “Listen well!”
Say no more about this demon: The Greek expression for say no more is literally “have no word.” This is obviously idiomatic, and subject to different interpretations. New Revised Standard Version say no more, Good News Translation “Don’t worry,” and New American Bible “do not give another thought” each give Raphael’s advice a slightly different color. The expression occurs again in verse 18. Here the expression is immediately connected with the quick, urgent command Take her. The two clauses together may have the force of “Don’t let the demon stand in your way! Go on! Marry her!”
I know: This is Raphael’s assurance to Tobias that he will have a wife before the night is out. It is not that there is some doubt and Raphael is trying to convince himself.
She will be given to you in marriage: See 3.17.
Quoted with permission from Bullard, Roger A. and Hatton, Howard A. A Handbook on Tobit. (UBS Helps for Translators). New York: UBS, 2001. For this and other handbooks for translators see here.