Musannaf Ibn Abi Shaybah

Hazrat Wa'il bin Hujr narrates that the Noble Prophet (peace and blessings be upon him) sat in prayer in such a way that he spread his left foot and kept his right foot upright.

Hazrat Aisha (may Allah be pleased with her) narrates that when the Prophet Muhammad (peace and blessings be upon him) would raise his head from prostration, he would not go into the second prostration until he had sat down completely. While sitting, he would spread his left foot underneath and keep his right foot upright.

Ibrahim narrates that when the Prophet Muhammad (peace and blessings be upon him) sat in prayer, he would lay out his left foot, to the extent that due to this practice, the outer part of his foot became darkened.

Hazrat Yazid bin Abdullah bin Qasit narrates that the Noble Prophet (peace and blessings be upon him) would lay down his left foot and keep his right foot upright.

Hazrat Ibn Umar (may Allah be pleased with them) narrates that the Sunnah of prayer is to spread the left foot and keep the right foot upright.

Hazrat Ka'b says that when you sit in prayer, spread your left foot, because in this there is more benefit for your prayer and your back.

Hazrat Harith narrates that Hazrat Ali (may Allah be pleased with him) used to keep his right foot upright and spread out his left foot.

Hazrat Hisham says that Hasan would sometimes spread both his feet and sometimes he would spread his right foot and keep his left foot upright. And when Muhammad sat in prayer, he would keep his right foot upright and spread his left foot.

The same statement is narrated through another chain of transmission.