Sayyiduna Tariq bin Abdullah al-Muharibi (may Allah be pleased with him) narrates: The Prophet (peace and blessings be upon him) said to me: "When you want to spit, do not spit to your right; rather spit to your left, if no one is there. And if someone is there, then spit under your foot."
Al-Bazzar recorded it, and its narrators are the narrators of the Sahih.
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الأدب / 13270