One of my favourite (Arab) proverbs:
وَكُلُّ يَدَّعِي وَصْلاً بِلَيْلَى **** وَلَيْلَى لَا تُقِرُّ لَهُمْ بِذَاكَا
إِذَا اشْتَبَكَتْ دُمُوعٌ فِي جُفُونٍ **** تبينَ مَنْ بَكَى مِمَّنْ تَبَاكَى
Shaykh al-Albani (رحمه الله) quoted it often (when referring to claimants of Islam/Sunnah and the truth). It is based on an old story of Arabic origin, about the 7th-century Najdi Bedouin poet Qays ibn al-Mullawah and his lady love Layla bint Mahdi (or Layla al-Aamiriya). “The Layla-Majnun theme passed from Arabic to Persian, Turkish, and Indian languages”, most famously through the narrative poem composed in 584/1188 by the Persian poet Nizami Ganjavi, as the third part of his Khamsa.