After Hudaybiyyah, when the truce freed the Prophet ﷺ to look beyond Arabia, he wrote to the rulers of the world, and the most famous of the letters went to Caesar. The emperor was Heraclius, who reigned from 610 to 641 and whom Muslim and non-Muslim historians alike remember kindly: a scholar of Christianity who tried and failed to reconcile its two great factions with a theology of his own, and a soldier who had just won back everything the Persians had taken, as Surah al-Rum had foretold when Rome seemed finished. Dihyah al-Kalbi carried the letter to the governor of Busra, where the Quraysh went to trade, to be sent on; and it happened that Heraclius was in Jerusalem, so it reached him at once. Abu Sufyan was trading in Busra, still a pagan, when a crier summoned him and his companions to Jerusalem, and he found himself standing in the palace of the emperor. Heraclius asked, through an interpreter, which of them was nearest in blood to the man who claimed to be a prophet. Abu Sufyan was, and was seated in front, his companions behind him with orders to signal if he lied. He said afterwards that only the fear of being called a liar by his own people made him tell the truth. The questions came one after another. His family? Noble. Had anyone among them claimed this before him? No. Had any of his ancestors been a king? No. Did the nobles follow him or the poor? The poor. Were they growing or shrinking? Growing. Did any leave his religion in disgust once they had entered it? No. Had he ever been accused of lying before he began? No. Did he break his word? No, though there was a truce between them now and no one knew what he would do, the one thing, Abu Sufyan admitted later, he could find to say against him. Had they fought him? Yes, and sometimes he won and sometimes they did. What did he command? To worship God alone and abandon the gods of their fathers, to pray, to speak the truth, to be chaste, and to keep the ties of kinship. Then Heraclius explained his questions. Prophets come from noble families. Had another made the claim before, this man might be imitating him; had his fathers been kings, he might be after his inheritance. A man who does not lie about money does not lie about God. The poor follow the prophets first, the truth always gains followers, and faith that has entered a heart and mingled with it is not thrown off. Prophets do not betray. And what he commanded was what the prophets had commanded. If all this was true, he said, the man would soon rule the ground beneath his feet; he had known from his scriptures that someone was coming, but had not expected him from the Arabs; and could he reach him, he would wash his feet. Then he called for the letter and had it read: in the name of Allah, from Muhammad ﷺ the servant of Allah and His Messenger ﷺ to Heraclius the great one of the Romans; peace on whoever follows guidance; submit and you will be safe and Allah will give you a double reward, and if you turn away you carry the sin of the Arisiyin; and the verse of Ali Imran calling the People of the Book to a word held in common, that none be worshipped but Allah. There was uproar in the court and the Arabs were put out. Abu Sufyan said to his companions on the way out that the affair of Ibn Abi Kabsha, the Quraysh's sneer for the Prophet ﷺ, had grown so great that the king of the Romans feared him; and it was there, he said, in the palace of Caesar, that Islam first entered his heart, three years before he embraced it. Sahih al-Bukhari keeps a second story of Heraclius, told apart from the first. He woke one morning troubled by a dream in which the king of the circumcised had appeared; his courtiers told him that only the Jews were circumcised and that he need only bear down on them. Then Dihyah arrived with the Prophet ﷺ's letter and, on examination, was found to be circumcised, and the emperor understood whom the dream meant. He wrote to a learned friend, a bishop, who wrote back that this was indeed the one; and it is likely, though the sources do not say it, that it was this friend who supplied the three tests Heraclius later sent the Tanukhi to make. At last he gathered his senators and asked what they thought of his following Muhammad ﷺ, and when they bolted for the doors he told them he had only been testing their faith. He died a Christian, in the confusion of a coup, having lived to see Jerusalem taken by the people of his dream.
Safiyyah was a girl in Madinah on the day the Prophet ﷺ arrived there, the favourite of her father Huyayy ibn Akhtab, chief of the Banu Nadir, and of her uncle Abu Yasir. She ran to them when they came home from seeing him and they walked past her, shoulders down, and she heard her uncle ask, is it him? and her father answer, by the Lord of Moses, it is him; and what then? we will oppose him as long as we live. She was exiled with her tribe and married in Khaybar, and when the Banu Nadir threw themselves into the front of Khaybar's defence more of them died than of Khaybar's own, her husband Kinana among them. She was a widow when the fighting ended, and a captive, and in the division she fell to Dihyah al-Kalbi. Companions said to the Prophet ﷺ that the daughter of the chief of the Banu Nadir should be his and not left to Dihyah, so he paid Dihyah her price and took her. No one knew at first whether he had taken her as a servant or a wife, so they watched. When it was time to leave Khaybar he couched his camel, knelt, and made his thigh a step for her to mount by, and she, out of respect, set her knee on it rather than her foot. Then he covered her with his cloak, and the Companions understood, for that veil was for his wives. Safiyyah did not yet know what it meant. When he went to her on the first night she refused him, and he let her be; a night's journey from Madinah she agreed, and he asked Umm Sulaym to make her ready. Umm Sulaym hung two cloths between trees and the women did what they could with what little they had, fretting that they had no perfume or jewellery for her, and when they had finished they smelt a scent finer than any they knew. When he entered he said the hard thing first: her father Huyayy had been the most open of the Jews in his enmity until Allah took him. It was a test of what was in her heart, and she answered from the Qur'an, that no soul bears the burden of another. Then he gave her the choice as she understood it, to accept Islam and stay with him, or to keep her faith and perhaps be freed and returned to her people. She said she had inclined to Islam before he offered it and had already believed in him; she had no people to go back to, her father and brother were gone; and Allah and His Messenger ﷺ were dearer to her than her own kin. He freed her, and her freedom was her dowry, and he married her. He had seen a bruise on her face and asked about it: her husband had struck her when she told him of a dream in which the moon rose from Yathrib and fell into her lap, and asked whether she expected the king of the Arabs to marry her. He had read the dream rightly. Asked afterwards why she had refused the first night, she said that so close to Khaybar she had feared the Jews would retaliate, and he loved her the more for it. Abu Ayyub al-Ansari stood outside the tent all night with his sword drawn, afraid of what a woman whose family had died at Muslim hands might do, and when the Prophet ﷺ found him there in the morning he laughed and prayed for him. The wedding feast was whatever anyone had, dates, a little clarified butter and barley mixed together. On the road, when the walls of Madinah came in sight and the riders whipped their camels forward as Madani custom was, the Prophet ﷺ's camel stumbled and threw them both; every Companion turned his face away, and only Abu Talha cried out to ask whether he was hurt. He was not, and he was on his feet at once with his cloak over her. In Madinah the wives came to look at her and Zaynab bint Jahsh said to Juwayriyya that this one would be trouble. She belonged to neither camp among them, having no family of her own, and perhaps that is why he was so tender with her. When Hafsa called her the daughter of a Jew and she wept, he asked why she had not answered that her father was a prophet, Harun, and her uncle a prophet, Musa, and her husband a prophet; on the Farewell Hajj he stopped speaking to Zaynab for refusing her a camel; and in his last illness, when Safiyyah wished she could take his fever on herself and the other wives murmured, he told them to rinse their mouths, for she had spoken the truth. She died in 52 AH.
Heraclius awoke troubled by a dream and an astrological omen that a leader of a circumcising people would arise and challenge him. His senators suggested it concerned only the Jews, but before he could act, Dihyah al-Kalbi arrived at his court with a message from the Prophet ﷺ and was found to be circumcised. Heraclius then wrote to a fellow scholar (most likely John IV). He later summoned his senators and asked what they thought of him embracing Muhammad ﷺ's faith; they reacted with fury, so he told them he was only testing their loyalty and remained upon his faith, dying some years later in the middle of a coup.