It is narrated from Sayyiduna Abu Hurayrah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "When one of you intends to offer voluntary prayer after offering the obligatory prayer, let him move a little forward or back, or to the right or left, and then pray."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3044