First: I have found nothing in the Sunnah showing that the Prophet ﷺ ever dispatched collectors to take alms from “hidden” assets—namely trade merchandise, gold, silver, or rikaz (buried treasure)—as the author himself asserts. Nor have I seen any hadith scholar mention such a practice. On the contrary, Ibn al-Qayyim expressly denies it, and he even limits the dispatching mentioned in the sources with regard to manifest assets, for he says in Zad al-Maʿad:

“The Prophet ﷺ used to send his collectors to the desert Bedouins; he did not send them to the villages. It was not part of his guidance ﷺ to send collectors except to the owners of manifest wealth—livestock, crops, and fruits.”

Had what the author claimed been authentic, it would constitute a Sunnah-based proof for the obligation of zakat on trade goods—so reflect on this.

Abu ʿUbayd records, no. 1644: “The settled Sunnah concerning al-ṣāmit (silent wealth: gold and silver) is that people are simply trusted with it.”

Second: I have likewise found no such practice among the three caliphs. Rather, Abu ʿUbayd (no. 1805) and al-Bayhaqi (4/114) narrate from Abu Saʿid al-Maqburi who said:

“I came to ʿUmar ibn al-Khattab and said, ‘Commander of the Faithful, this is the zakat of my wealth’—and I had brought him two hundred dirhams. He asked, ‘Have you freed any slaves, O Kaysan?’ I replied, ‘Yes.’ He said, ‘Then take it back and distribute it yourself.’”

Its chain is sound. Thus ʿUmar—may Allah be pleased with him—placed the distribution of zakat in the hands of its owner, contrary to what the author reports of him. Al-Bayhaqi labels this narration, “Chapter: A man personally distributes the zakat of his hidden wealth.”

Third: As for what he cites from ʿUthman—that the latter continued on the same course—I have found no basis for it.