Hausa Folk-Lore, by Maalam Shaihua, tr. by R. Sutherland Rattray, [1913], at sacred-texts.com
18. The story of Muusa (Moses) and how it came about that brothers and sisters do not marry each other
This story is about (a boy called) Musa.
A story, a story. Let it go. Let it come.
A certain chief begat children, two in number, a girl and a boy. They grew up. A husband was found for her, the daughter, (but) she said she did not want him; only her big brother she loved. If she was told to go and call Musa, then she went, (and) said, 'What's-your-name, they say you are to come.' And it was always so, (till) one day her brother said, 'I shall cure her of that.' (Lit. I shall make its medicine.)
There was a small stream at their village, the children used to bathe in it when the sun was up; there was a tree in the middle of the stream at their village where the girls used to fasten their little loincloths. And Musa waited in the meantime.
When they had come (and) entered the water (and) bathed they laid aside their loin-cloths at the water's edge. Then he (Musa), came and took them all away, and went and climbed the tree in the middle of the water (middle of the water), each one who came out did not see his (her) cloth, whereupon he (she) began to cry.
And Musa was up above and watching till they all came out. He said, 'All of you, see, your cloths are with me. Whoever calls out my name, I will give him (her) his (her) cloth; otherwise I will not give you.' Then one girl came forward. She said, 'You, Musa, you, Musa, Musa the spiteful one, Musa the son of chiefs, for Allah's sake, Musa, give me my loin-cloth.' And he gave her (it). And so on, and so on, until they all received from him their cloths, and there was only left his little sister.
And she was told, 'Go and get your cloth.' Now the water was up to the ankles. Then she entered the water (and) said, 'You, Musa, Musa, the spiteful one, Musa the son of chiefs, for Allah's sake, Musa, give me my loincloth.' But Musa said 'I do not give it to you till you have said it again, then I will give it to you.'
Now she has forgotten (for a minute that she would not say his name); when she remembered, then she said, 'You, What's-your-name, you, What's-your-name, What's-your-name the spiteful one, What's-your-name the son of chiefs, for the sake of Allah, What's-your-name, give me my cloth.'
But he said, 'I have refused to give you, I have refused to give you, till you say, You, Musa, you, Musa, Musa the spiteful one, Musa the son of chiefs, for the sake of Allah, Musa, give me my cloth.' Now by this time the water was up to her shins. Then she said, 'You, What's-your-name, you, What's-your-name, What's-your-name the spiteful one, What's-your-name the son of chiefs, for Allah's sake, What's-your-name, give me my loin-cloth.'
But now the water had reached her thighs. But Musa said, 'I have refused to give you unless you have said, You, Musa, Musa the spiteful one, Musa the son of chiefs, for the sake of Allah, Musa, give me my cloth.' She said, 'You, What's-your-name, you, What's-your-name, What's -your-name, the spiteful one, What's-your-name the son of chiefs, for the sake of Allah, What's your name, give me my loin-cloth.'
But Musa said, 'I have refused to give you, I have refused to give you, unless you say, You, Musa, you, Musa, Musa the spiteful one, Musa the son of chiefs, for the sake of Allah, Musa, give me my cloth.' And the water reached to her breasts, but she said, 'You, What's-your-name, you, What's-your-name, What's-your- name, the spiteful, What's-your-name the son of chiefs, for Allah's sake, What's -your-name, give me my cloth.'
But Musa said, 'I have refused to give you till you have called out my name.' And the water was up to her neck. And they said, 'Speak his name; if you do not speak the water will swallow you up.' Now the water was trying hard to reach her chin. Then she said, I You, Musa, you, Musa, Musa the spiteful one, Musa the son of chiefs, for the sake of Allah, Musa, give me my cloth.' But he said, 'Repeat it.' She said it (again).. He said, 'Again.' She repeated it, until three times. He said, 'Are you going to say again that I am your husband?' She said, 'No.' 'Do you want the husband whom you have been given?' She said, 'Yes.'
This was the beginning (of the custom) that a brother should not marry his sister.
That is all.
Off with the rat's head.