Al-Matalib al-'Aliyah 3265 — Prohibition of hair-splitting

Ishaq relates that he asked Abu Usamah: Did Mis'ar narrate this hadith to you? He related that Ma'n bin Abd al-Rahman showed me a piece of writing and swore that it was in the handwriting of his father (Abd al-Rahman bin Abdullah bin Mas'ud), and in it was written that Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) said: 'Wa alladhi la ilaha ghayruhu' "By the One besides whom there is no true god! I have not seen anyone more concerned and fearful about the outcome of those who go to extremes and split hairs (al-mutanatti'in) than the Messenger of Allah (peace and blessings be upon him), and after the Messenger of Allah (peace and blessings be upon him) there was no one more fearful concerning them than Sayyiduna Abu Bakr (may Allah be pleased with him), and I think that Sayyiduna Umar (may Allah be pleased with him) was the most fearful for them or of their trial."
At this Abu Usamah confirmed it, saying: Yes! Imam Abu Bakr and Imam Abu Ya'la also narrated it from Abu Usamah, each with his own chain.