A Comprehensive Compilation of Reliable Narrations · Hadith 495 (#Ḥadīth #8)

[-/8] الكافي: محمد بن يحيى، عن أحمد بن محمد، عن الحسين بن سعيد، عن النضر بن سويد عن عاصم بن حميد (رفعه) (قال:) قال: سئل علي بن الحسين عليه السلام عن التوحيد فقال: إن الله عزوجل علم أنه يكون في آخر الزمان أقوام متعمقون فأنزل الله تعالى قُلْ هُوَ اللَّهُ أَحَدٌ والآيات من سورة الحديد إلى قوله: وَهُوَ عَلِيمٌ بِذَاتِ الصُّدُورِ فمن رام وراء ذلك فقد هلك

8. [8/-] al-Kafi: Muhammad b. Yahya from Ahmad b. Muhammad from al-Husayn b. Sai’d from al-Nadhr b. Suwayd from A’sim b. Humayd who raised it - he said: Ali b. al-Husayn عليه السلام was asked about Tawhid (Unity of God) so he said: Allah Mighty and Majestic knew that there would in the last age peoples who delve deep (wanting to know) so Allah the Elevated brought down “Say: He is Allah One” (chapter 112) and the verses in Surat al-Hadid until His words “and He is Knowing of that within the hearts” (57:6) so whoever looks (desires) beyond that then he has perished.

Gradings are classical jarḥ-wa-taʿdīl, name-matched to a rijāl index (not individually re-verified).