Sayyiduna Abu Hurayrah (may Allah be pleased with him) narrates that the Messenger of Allah (peace and blessings be upon him) said: "When one of you is praying, let him not spit in front of him, for he is facing his Lord, the Possessor of honour and greatness; nor to his right. Rather, let him spit to his left or under his left foot. If he is not able to, then let him spit into the edge of his garment, then rub the garment together."
Sayyiduna Abu Hurayrah (may Allah be pleased with him) said: It is as if I am looking at the Messenger of Allah (peace and blessings be upon him) rubbing his garment together.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3593