‘…shall do so in a known measure, a known weight, and a known term.’

Authentic (Sahih). Narrated by Muslim in (Al-Musaqat, h/ 127, 128 repeated), Al-Nasa'i (7/290), Ibn Majah (h/ 2280), Al-Tirmidhi (h/ 1311, 1321), Abu Dawud in (Al-Buyu', chapter “57”), Al-Tabarani (11/230), Al-Daraqutni (3/3), Al-Manthur (1/370), Talkhis (3/32), Ithaf (5/451), Sharh al-Sunnah (8/173), and Ibn Kathir (1/496).

556: 2955: With justice: 1: Ibn Kathir said: One who knows how to write should not refrain when asked to write for people, and there is no hardship upon him in that. Just as Allah taught him what he did not know, he should show charity to others who do not know how to write. He should write as it came in the hadith: “Indeed, it is an act of charity to help a craftsman or to do work for a clumsy person.”

Narrated by Ibn Kathir: (1/335).

And in the other hadith: “Whoever conceals knowledge that he knows will be bridled on the Day of Resurrection with a bridle of fire.”

Weak (Da'if). Narrated by Ahmad (2/499), Ithaf (1/104), Al-Kanz (29149), Ibn Kathir (1/497), Al-Khafa' (2/377), and Tadhkirah (26).

And Shaykh Al-Albani declared it weak. Da'if al-Jami'.

(h/ 5814 p/ 839).