It is narrated from Hazrat Shuraid (may Allah be pleased with him) that whenever the Noble Prophet (peace and blessings be upon him) saw a man lying on his face in such a way that there was nothing on his buttocks, he would strike him with his foot and say: "This way of lying down is the most disliked by Allah."
Hadith Referenceمسند احمد / تتمہ مُسْنَدِ الْكُوفِيِّينَ / 19458
Hadith Gradingحکم دارالسلام:مرفوعه حسن لغيره، وهذا اسناد مرسل