Ibn Athīr Al-Jaza'iri (Died 630 AH) quoted a narration under the heading of a Companion of Prophet (ﷺ) - Abdur Rahman bin Mudlaj as follows :
عبد الرحمن بن مدلج أورده ابن عقدة. وروى بإسناده، عن أبي غيلان سعد بن طالب، عن أبي إسحاق، عن عمرو ذي مر، ويزيد بن يثيع وسعيد بن وهب، وهانئ بن هانئ، قال أبو إسحاق: وحدثني من لا أحصي أن علياً نشد الناس في الرحبة من سمع قول رسول الله صلى الله عليه وسلم: «من كنت مولاه فعليٌّ مولاه، اللهم وال من والاه وعاد من عاداه»، فقام نفر شهدوا أنهم سمعوا ذلك من رسول الله صلى الله عليه وسلم وكتم قوم، فما خرجوا من الدنيا حتى عموا، وأصابتهم آفة، منهم: يزيد بن وديعة، وعبد الرحمن بن مدلج. أخرجه أبو موسى
Abdur Rahman bin Mudlaj : Ibn Uqdah quoted from him. He narrated via his chain....., Abu Ishaq said : countless people have told me that Ali (as) called upon people to testify in Al-Rahbah that whoever has heard from Prophet (ﷺ) : Whoever I am his Mawla this ‘Ali is his Mawla. Oh Allah, love whoever loves him and be hostile to whoever is hostile to him", Some men stood up and testified that they heard from Prophet (ﷺ) like this and a large group hide it. They didn't left this world untill became blind and calamaties befall upon them and among them were Yazid bin Wade'yah, Abdur Rahman bin Mudlaj. This has been narrated by Abu Mūsa.
Āsad ul Ghaba - Ibn Athīr // Volume 3 // Page 487 // Edn. Dar ul Kutub Al-Ilmiyyah Beriut Lebanon.
Same narration from Ibn Uqdah is quoted by Dahabhi (Died 748 AH) and there he metioned it completely.
The same narration is found in the manuscript of this Risalah which is present in Central Libriary of Tehran University under number 1080.
Now when the same narration was quoted by Ibn Hajr Asqalani (Died 852 AH) he changed the text and made following changes :
1. He hide the name of one companion Yaxid bin Wade'yah from narration who was involved with hiding the truth.
2. In actual narration Abdur Rahman bin Mudlaj was from those who had hidden this narration when asked to testify, Ibn Hajr changed the text and made it to look that this Abdur Rahman bin Mudlaj was one of those who even testified - STRANGE.
3. He also erased out last part of narration " Oh Allah love whoever loves him and be hostile to whoever is hostile to him
Al-Isabah fi Tameez Sahabah - Ibn Hajr // Volume 6 // Page 564 // Edn. Riyadh Saudi Arabia.