The Peak of Eloquence · Hadith 1414 (#Passage #223)
Chapter 44 | To Ziyad ibn Abeen, when Ali learned that Muawiya had approached him
فَلَمَّا قَرَأَ زِيَادٌ الْكِتَابَ قَالَ: شَهِدَ بِهَا وَرَبِّ الْكَعْبَةِ، وَلَمْ تَزَلْ فِي نَفْسِهِ حَتَّى ادَّعَاهُ مُعَاوِيَةُ.
(as-Sayyid ar-Raḍī says:) When Ziyād read this letter he said, “By Allāh he has testified to it.” This point remained in his mind till Mu‘āwiyah claimed him (as his brother by his father).
Gradings are classical jarḥ-wa-taʿdīl, name-matched to a rijāl index (not individually re-verified).