Ibn Umar (may Allah be pleased with them both) was at a water (spring) of his when news reached him that Husayn bin Ali (may Allah be pleased with them both) was heading for Iraq, so he caught up with him. (The narrator) mentioned the long hadith in which he told him to turn back, but he refused to turn back. Ibn Umar (may Allah be pleased with them both) embraced him, wept and said: 'Astawdi'uka Allaha min qatil' (I entrust you to Allah, fearing that you will be slain).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النكاح / 13574