The chapter
Rajab, 9 AH, high summer, the fruit ripening, the year's worst season for war. Word came of a Byzantine mobilization on the Syrian frontier, and for the first time the Prophet ﷺ announced a campaign's destination openly: Tabuk, weeks of desert north. There would be no ambiguity and no shade, the Qur'an named the whole episode "the hour of hardship."
The muster became a public test of hearts. Uthman equipped the army of hardship almost single-handedly, a thousand dinars poured into the Prophet's lap, drawing the words: "Nothing will harm Uthman after what he has done today." Abu Bakr brought his entire wealth; asked what he left his family, he answered: "Allah and His Messenger." The poor came weeping, the Qur'an records them, turned away because no mounts remained, "their eyes overflowing with tears of grief that they could not find something to spend." Meanwhile the hypocrites manufactured excuses with fatwa-grade creativity: "Do not march in the heat," to which the answer came down: "Say: the fire of Jahannam is more intense in heat."
Thirty thousand marched. Ali was left over Madinah, stung by the gossip of hypocrites until the Prophet ﷺ set his rank with one sentence: "Are you not content to be to me as Harun was to Musa, except that there is no prophet after me?"
At Tabuk there was no battle: the Byzantine force did not materialize. The army held the frontier for some twenty nights, secured treaties with the border statelets, and turned home, past the mosque the hypocrites had built as a rival gathering point, which revelation ordered demolished: "a masjid of harm and disbelief," the anti-Quba.
The deepest chapter of Tabuk belongs to the three believers who simply failed to set out, no hypocrisy, no excuse. Ka'b ibn Malik told his own story in the long hadith of Bukhari: how lying was easy and he refused it; how the Prophet ordered the community to withhold speech from the three; how fifty days of social death narrowed the earth "vast as it is" upon them; how even the letter from a foreign king offering him asylum went into the fire; and how forgiveness descended at dawn from above seven heavens: "…and to the three who were left behind, until the earth closed in on them for all its vastness, and their souls closed in on them, and they knew there was no refuge from Allah except in Him, then He turned to them, that they might repent." Ka'b said: I have never known a day better than that day.
Tabuk was the last expedition of his life ﷺ. On the return road, at every hard pass, the community had learned the campaign's single lesson in three registers, money, marching, and truth-telling: the religion is proven in the season when it costs.