Not Osiris. Horus the younger.
...Set said to Horus, "Come — If we are to have peace between our two lands then we must lay down beside each other in bed." Horus, too drunk on beer to disagree, went to sleep facing East, as Set went to sleep facing West...
But during the night, Set caused his phallus to become stiff and inserted it between Horus’ thighs. Then Horus, in his sleep, placed his hands between his thighs and received Set’s semen.
Early the next morning, Horus went to show his mother Isis what had been done to him: "Help me, Isis, my mother. Come and see what Set has done to me." He opened his hands and let her see Set’s semen. She let out a loud shriek, seized a copper knife, cut off his hands, and discarded them into the river. Then she fetched some fragrant ointment and applied it to Horus’ phallus. She caused it to become stiff and inserted it into a pot, and he caused his semen to flow down into it.
That morning, Isis carried the semen of Horus to the garden of Set. She asked Set’s gardener, "What sort of vegetable is it that Set eats here in your company?"
The gardener replied, "He doesn’t eat any vegetable here in my company except lettuce."
That being said, Isis walked into the lettuce garden with the jar and added the semen of Horus onto it.
Soon Set arrived, according to his daily habit, and ate the lettuce. This made him become pregnant with the semen of Horus.
Later that morning, Set went up to Horus: "Come. Let’s go to council so that I may contend with you in the tribunal." Horus agreed.
They both went to the tribunal and stood in the presence of the Great Ennead. They were told to speak concerning themselves.
Set started: "Let me be awarded the office of ruler. Horus, the one who is standing trial, has received the labor of a male against him that I have performed." The Ennead let out a loud cry. They spewed and spat at Horus’ face. But Horus laughed at them.
Horus then took an oath by gods as follows: "All that Set has said is false. Let Set’s semen be summoned that we may see from where it answers, and my own be summoned that we may see from where it answers."
Then Thoth, lord of script and scribe of truth for the Ennead, put his hand on Horus’ shoulder and said: "Come out, you semen of Set."
It answered him, but from the distant water in the interior of the marsh. Thoth put his hand on Set’s shoulder and said: "Come out, you semen of Horus."
Then it said to him: "Where shall I come from?"
Thoth said to it: "Come out from his ear."
Horus’ semen questioned Thoth: "is it from his ear that I should issue forth, seeing that I am divine seed?"
Then Thoth said to it: "Come out from the top of his head." Suddenly, it emerged as a golden solar disk upon Set’s head. Set became exceeding furious and extended his hands to seize the golden solar disk, but Thoth took it away from him and placed it as a crown upon his own head.
Then the Ennead agreed: "Horus is right, and Set is wrong."
I love ancient mythology!