It was then, seeing his brave warriors beginning to stagger, that he called a halt. All his men, worn out by fatigue, dropped on the ground, overcome by deep sleep where they fell, without having been able to give vent to the feelings of fury seething in their hearts and which might have caused most sanguinary conflicts among them. The "Hypocrite" Abdullah had a son who was also called Abdullah. He was a sincere Believer and he went to the Prophet. 'They tell me,' quoth the young man, 'that thou didst intend to kill Abdullah, my father. In that case, charge me to bring thee his head, for by Allah! thou shalt know that among the Khazraj, there is no son more devoted to his father than I. If thou shouldst charge any other to execute him, I should not be able to bear the sight of his murderer going unpunished and I should kill him. Therefore I should be slaying a true Mussulman in order to avenge a Mussulman "Hypocrite," and render myself deserving of hell-fire.' The Prophet tranquilised the stoical Believer by these words: 'Give no credit to what thou didst hear. On the contrary, we look upon thy father as our friend and comrade, so long as he remaineth with us.' [Sidenote: THE TAYANNUM, OR THE CEREMONY OF ABLUTION PERFORMED WITH SAND] It was during this expedition that the following Revelation came down: "_But if ye are sick, or on a journey, or if one of you come from the place of retirement, or if ye have touched women and find no water, then take clean sand and rub your faces and your hands with it._" (THE QUR'AN, V, 9.) Thus was established the Tayammum, or purification by sand, destined to prevent the Believers from ever forgetting their salutary duty; for this did away with the pretext, so frequent in their deserts, that lack of water hindered the performance of ablutions. [Sidenote: THE BATTLE OF THE DITCH (_Year V of the Hegira, A.D. 627_)] A deputation of Jews from the tribe of the Banu Nazir, and a few malcontents of the Wayls journeyed to Makkah to offer the Quraish an alliance. The Ghatafans, a tribe hailing from the north of the Hijaz, and the "Habash," or Arab Confederates, joined them. Thus was organised a vast conspiracy, threatening Al-Madinah on all sides. This time, when the Prophet got to hear of the importance of this expedition, he had no difficulty in persuading the Believers that the only way to save themselves was by entrenchment in the town and there awaiting the advent of the enemy.