Where is this hadith attested "He who knows himself knows his Lord"?

Question

I've read that the following:

He who knows himself knows his Lord

is a hadith. Where is it attested?

Answer 1

The saying you are referring to:

من عرف نفسه فقد عرف ربه

He who knows himself knows his Lord

This is not a hadith attributed to the Prophet ﷺ, but it is a saying attributed to Yahya ibn Mu'ādh ar-Rāzi as:

• Shams ad-Dīn as-Sakhāwi mentioned in his book Al-Maqāsid al-Hassana, Vol. 2, pp. 657 as attested by Al-Hāfidh Abu Sa'd as-Sam'āni
• Ibn Hajar al-Haytami in his book Al-Fatāwa al-Hadīthiyya, pp.206.

There are numerous other scholars that said this hadith is a fabricated one (e.g., Ibn Taymiyyah, Ismā'īl al-'Ajalōni, etc.)

Answer 2

In some references, it is referred to as a saying of The Prophet (pbuh) and in some others it is considered as a hadith from Imam Ali (A.S.). But in both cases consequence of the people who narrate this hadith is not mentioned (This hadith is a Morsal ‍‍مُرسَل), although the concept of this statement is true.