It is narrated from Shahr bin Hawshab: We were going with Sayyiduna Ibn Umar (may Allah be pleased with them), when his (son) Salim said to him: Abu Abdur Rahman! The time for prayer has come.
It is narrated from Abdullah bin Dinar, who reports from Sayyiduna Ibn Umar (may Allah be pleased with them both), that he (Ibn Umar) once said: But Abu Hafs (Sayyiduna Umar, may Allah be pleased with him) made this decision.