(a) Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) narrates: None of you should leave any part of his prayer for Satan, that is, by turning away only to the right (rather, he should turn to the left as well).
I have seen the Messenger of Allah (peace and blessings be upon him) many times turning away to the left (too).
(b) These are the words of the hadith of Shu'bah (may Allah have mercy on him). In the hadith of Abu Usamah (may Allah have mercy on him), "juz'an" (a part) appears in place of "nasiban" (a share), and "'an shimalihi" appears in place of "'an yasarihi" (both meaning: to his left).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3610