It was said: “O Messenger of Allah, what is wealth?” He said: “Fifty dirhams, or their equivalent in gold.”(1)

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(1) The hadith is authentic, but this chain of transmission is weak due to the weakness of Hakim ibn Jubayr. However, Zubayd al-Yami—who is trustworthy—corroborated him, as recorded by the compiler, Ibn Majah, and al-Nasa’i. Ahmad ibn Hanbal cited this hadith as evidence, as reported by Ibn ‘Adi in al-Kamil 2/636. Al-Thawri, Ishaq ibn Rahawayh, al-Hasan ibn Salih, and Ibn al-Mubarak also cited it as evidence, as al-Tirmidhi related from them after the hadith (657), and Ibn ‘Abd al-Barr in al-Tamhid 4/101–103. Ibn al-Turkumani declared it authentic in al-Jawhar al-Naqi 7/24–25. Sufyan is al-Thawri.
Ibn Majah (1840), al-Tirmidhi (657), and al-Nasa’i in al-Kubra (2384) also transmitted it via multiple routes from Yahya ibn Adam, with this chain.
Al-Tirmidhi (656) also transmitted it via the route of Sharik, from Hakim ibn Jubayr, with it.
It is in Musnad Ahmad (3675). It has supporting witnesses; see them there.
Al-Khattabi said: “Al-khumush are scratches. It is said: ‘A woman khammashat her face,’ meaning she scratched it with a nail, a piece of iron, or something similar. Al-kuduh are the marks left by scratches, bites, and the like.”
Al-Tirmidhi said: “The practice is according to this with some of our companions, and al-Thawri, ‘Abdullah ibn al-Mubarak, Ahmad, and Ishaq hold this view. They said: If a man has fifty dirhams, charity is not permissible for him. Some scholars did not adopt the hadith of Hakim ibn Jubayr and were lenient in this matter. They said: If he has fifty dirhams but is in need, he may take from the zakat. This is the view of al-Shafi‘i and other scholars.”
See also Sharh al-Sunnah by al-Baghawi 6/85–86, in our critical edition.
Al-Bayhaqi said in Ma‘rifat al-Sunan wa al-Athar (13337), after citing the hadiths on the permissibility of asking and the limit of wealth that permits asking: “All of this agrees in meaning, namely that wealth—which is sufficiency—is what is considered. Then it varies according to people: some are made wealthy by fifty, some by forty, and some have an income that provides for them each day, feeding them morning and evening, with no dependents—such a person is self-sufficient and it is not permissible for him to receive charity.” See the rest of his words in Ma‘rifat al-Sunan wa al-Athar 9/330–331.