Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) said: I was present with my father when he was struck (wounded). They praised him and said: "May Allah reward you with good." He said: "(People are) hopeful and fearful." They said: "Nominate a successor." He said: "Shall I bear your affair both in life and in death? I wish that my share of it were just enough to break even, nothing against me and nothing for me. If I nominate a successor, then one better than me nominated a successor; and if I leave you, then one better than me left you, the Messenger of Allah (peace and blessings be upon him)." Abdullah said: So I knew, when he mentioned the Messenger of Allah (peace and blessings be upon him), that he would not nominate a successor.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب قتال أهل البغي / 16571