The History Of Herodotus Volume 1 of 2
Page: 14929. When the priests had brought Apis, Cambyses being somewhat affected with madness drew his dagger, and aiming at the belly of Apis, struck his thigh: then he laughed and said to the priests: "O ye wretched creatures, are gods born such as this, with blood and flesh, and sensible of the stroke of iron weapons? Worthy indeed of Egyptians is such a god as this. Ye however at least shall not escape without punishment for making a mock of me." Having thus spoken he ordered those whose duty it was to do such things, to scourge the priests without mercy, and to put to death any one of the other Egyptians whom they should find keeping the festival. Thus the festival of the Egyptians had been brought to an end, and the priests were being chastised, and Apis wounded by the stroke in his thigh lay dying in the temple.
30. Him, when he had brought his life to an end by reason of the wound, the priests buried without the knowledge of Cambyses: but Cambyses, as the Egyptians say, immediately after this evil deed became absolutely mad, not having been really in his right senses even before that time: and the first of his evil deeds was that he put to death his brother Smerdis, who was of the same father and the same mother as himself. This brother he had sent away from Egypt to Persia in envy, because alone of all the Persians he had been able to draw the bow which the Ichthyophagoi brought from the Ethiopian king, to an extent of about two finger-breadths; while of the other Persians not one had proved able to do this. Then when Smerdis had gone away to Persia, Cambyses saw a vision in his sleep of this kind:—it seemed to him that a messenger came from Persia and reported that Smerdis sitting upon the royal throne had touched the heaven with his head. Fearing therefore with regard to this lest his brother might slay him and reign in his stead, he sent Prexaspes to Persia, the man whom of all the Persians he trusted most, with command to slay him. He accordingly went up to Susa and slew Smerdis; and some say that he took him out of the chase and so slew him, others that he brought him to the Erythraian Sea and drowned him.
31. This they say was the first beginning of the evil deeds of Cambyses; and next after this he put to death his sister, who had accompanied him to Egypt, to whom also he was married, she being his sister by both parents. Now he took her to wife in the following manner (for before this the Persians had not been wont at all to marry their sisters):—Cambyses fell in love with one of his sisters, and desired to take her to wife; so since he had it in mind to do that which was not customary, he called the Royal Judges and asked them whether there existed any law which permitted him who desired it to marry his sister. Now the Royal Judges are men chosen out from among the Persians, and hold their office until they die or until some injustice is found in them, so long and no longer. These pronounce decisions for the Persians and are the expounders of the ordinances of their fathers, and all matters are referred to them. So when Cambyses asked them, they gave him an answer which was both upright and safe, saying that they found no law which permitted a brother to marry his sister, but apart from that they had found a law to the effect that the king of the Persians might do whatsoever he desired. Thus on the one hand they did not tamper with the law for fear of Cambyses, and at the same time, that they might not perish themselves in maintaining the law, they found another law beside that which was asked for, which was in favour of him who wished to marry his sisters. So Cambyses at that time took to wife her with whom he was in love, but after no long time he took another sister. Of these it was the younger whom he put to death, she having accompanied him to Egypt.