Tobit 6:15-22

15 Now I am afraid, lest the same thing should happen to me also: and whereas I am the only child of my parents, I should bring down their old age with sorrow to hell.
16 Then the angel Raphael said to him: Hear me, and I will shew thee who they are, over whom the devil can prevail.
17 For they who in such manner receive matrimony, as to shut out God from themselves, and from their mind, and to give themselves to their lust, as the horse and mule, which have not understanding, over them the devil hath power.
18 But thou when thou shalt take her, go into the chamber, and for three days keep thyself continent from her, and give thyself to nothing else but to prayers with her.
19 And on that night lay the liver of the fish on the fire, and the devil shall be driven away.
20 But the second night thou shalt be admitted into the society of the holy Patriarchs.
21 And the third night thou shalt obtain a blessing that sound children may be born of you.
22 And when the third night is past, thou shalt take the virgin with the fear of the Lord, moved rather for love of children than for lust, that in the seed of Abraham thou mayst obtain a blessing in children.
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