Sayyiduna Abu Sa'id Khudri (may Allah be pleased with him) narrates that the Prophet Muhammad (peace and blessings be upon him) saw phlegm stuck in the direction of the qiblah in the mosque, so he scraped it off with a pebble. And the Prophet (peace and blessings be upon him) forbade spitting in front of oneself or to one's right side (during prayer). The Prophet (peace and blessings be upon him) said: "(The one praying) should spit to his left side or under his left foot."