A man from Banu Mudlij narrates from his father: Sayyiduna Suraqah bin Malik (may Allah be pleased with him) came back (to his people) from the Prophet (peace and blessings be upon him) and said: The Prophet (peace and blessings be upon him) has taught us such and such things. A man said by way of mockery: Has he also taught you how you should relieve yourselves? Sayyiduna Suraqah (may Allah be pleased with him) replied: Yes indeed! By the One who sent him with the truth, he commanded us that (while relieving ourselves) we should put our weight on the left foot and keep the right foot raised.
Al-Tabarani recorded it in al-Mu'jam al-Kabir; its chain contains a man who has not been named.
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الطهارة / 1020