Musannaf Ibn Abi Shayba 3:6479

Ibn ‘Ulayyah narrated to us, from Ibn ‘Awn, who said: It was said to al-Hasan, "They say that it is disliked for a man to pray while he has taken his hand out from under his garment (at his chest)." Al-Hasan said, "If Allah had entrusted His religion to these people, they would have constricted His servants."