It is narrated from Sayyiduna Abu Hurairah (may Allah be pleased with him), the Noble Prophet (peace and blessings be upon him) said: "It is not permissible to cause deficiency in the (acts of) prayer, nor to give salam (greeting of peace) during the prayer."
Hadith Referenceسلسله احاديث صحيحه / الاذان و الصلاة / 809