The warlike expeditions to which Ḥassán devoted all his energy were felt as an intolerable burden by the chiefs of Ḥimyar, who formed a plot to slay him and set his brother ‘Amr on the throne. ‘Amr was at first unwilling to lend himself to their designs, but ultimately his scruples were overcome, and he stabbed the Tubba‘ with his own hand. The assassin suffered a terrible punishment. Sleep deserted him, and in his remorse he began to execute the conspirators one after another. There was, however, a single chief called Dhú Ru‘ayn, who had remained loyal and had done his best to save ‘Amr from the guilt of fratricide. Finding his efforts fruitless, he requested ‘Amr to take charge of a sealed paper which he brought with him, and to keep it in a safe place until he should ask for it. ‘Amr consented and thought no more of the matter. Afterwards, imagining that Dhú Ru‘ayn had joined in the fatal plot, he gave orders for his execution. "How!" exclaimed Dhú Ru‘ayn, "did not I tell thee what the crime involved?" and he asked for the sealed writing, which was found to contain these verses-- "O fool to barter sleep for waking! Blest Is he alone whose eyelids close in rest. Hath Ḥimyar practised treason, yet 'tis plain That God forgiveness owes to Dhú Ru‘ayn.[69]" On reading this, ‘Amr recognised that Dhú Ru‘ayn had spoken the truth, and he spared his life. [Sidenote: Dhú Nuwás.] [Sidenote: Massacre of the Christians in Najrán (523 A.D.).] [Sidenote: Death of Dhú Nuwás.] With ‘Amr the Tubba‘ dynasty comes to an end. The succeeding kings were elected by eight of the most powerful barons, who in reality were independent princes, each ruling in his strong castle over as many vassals and retainers as he could bring into subjection. During this period the Abyssinians conquered at least some part of the country, and Christian viceroys were sent by the Najáshí (Negus) to govern it in his name. At last Dhú Nuwás, a descendant of the Tubba‘ As‘ad Kámil, crushed the rebellious barons and made himself unquestioned monarch of Yemen. A fanatical adherent of Judaism, he resolved to stamp out Christianity in Najrán, where it is said to have been introduced from Syria by a holy man called Faymiyún (Phemion). The Ḥimyarites flocked to his standard, not so much from religious motives as from hatred of the Abyssinians. The pretended murder of two Jewish children gave Dhú Nuwás a plausible _casus belli_. He marched against Najrán with an overwhelming force, entered the city, and bade the inhabitants choose between Judaism and death. Many perished by the sword; the rest were thrown into a trench which the king ordered to be dug and filled with blazing fire. Nearly a hundred years later, when Muḥammad was being sorely persecuted, he consoled and encouraged his followers by the example of the Christians of Najrán, who suffered "_for no other reason but that they believed in the mighty, the glorious God_."[70] Dhú Nuwás paid dearly for his triumph.