Sayyiduna Zayd bin Khalid al-Juhani (may Allah be pleased with him) narrates that Sayyiduna Umar bin al-Khattab (may Allah be pleased with him), who was the Caliph at the time, saw him pray two rak'ahs after Asr. Sayyiduna Umar (may Allah be pleased with him) walked over to him and struck him with the whip, but he carried on praying. When he finished his prayer, Sayyiduna Zayd (may Allah be pleased with him) said: "O Commander of the Faithful! By Allah, after having seen the Prophet (peace and blessings be upon him) pray these two rak'ahs, I will never abandon them." The narrator said: Sayyiduna Umar (may Allah be pleased with him) then sat down with him and said: "O Zayd bin Khalid! Were it not that I fear people would take this as a ladder to prayer until night falls (that is, they would keep praying continuously until Maghrib), I would not strike anyone over these two rak'ahs."
Ahmad and al-Tabarani in al-Mu'jam al-Kabir recorded it, and its chain is hasan (good).