Musannaf Ibn Abi Shayba 2:192

Hussain bin Ali narrated to us, from Abu Musa, who said: When those who make the call to prayer at night were mentioned in the presence of Al-Hasan, he said: "It is said: They are idle non-Arabs who do not pray the iqamah. If Umar ibn al-Khattab had caught them, he would have beaten them painfully, or he would have beaten their heads painfully."