18:19 Now send one of you forth with this silver of yours to the city, and let him look to which of them has the purest food.
Here there are two allusions: One is that every faithful servant, though he may have reached the furthest limit in the Haqiqah, will be held to guarding the rulings of the Shariah, for any reality in which the outward Shariah is not witnessed is the deception and delusion of Satan. The root in this is that the chevaliers sent one of themselves to buy some food for them, and they commanded him to investigate and scrutinize its situation so that heedlessness would not make him fall into something forbidden.
The second is what was said by Yūsuf ibn al-Ḥusayn to one of his companions when he took something to the poor or to the folk of recognition, or when he bought food for them: “Let it be the most goodly and the most subtle of things, for when someone reaches recognition, only subtle things conform with him and only delicate things become his intimate. The root here is His words, 'and let him look to which of them has the purest food.'” Then he said, “When you buy for the renunciants and the worshipers, buy whatever you find, for they are still busy with abasing their own souls and holding them back from appetites.”