´Suhaib narrated:` "I passed by Allah's Messenger (S) while he was performing Salat, so I said greeted him with Salam, and he returned it by making signals." He said: "I do not know except that he said: 'He indicated with his finger.'"
´Ibn Umar narrated:` "I said to Bilal: 'How did the Prophet (S) reply to them when they gave him Salams and he was performing Salat?' He said: 'He would motion with his hand.'"
Hadith Referenceسنن ترمذي / كتاب الصلاة / 368
Hadith Gradingالألبانی:صحيح، ابن ماجة (1017)
Hadith Takhrij«سنن ابی داود/ الصلاة 170 (925) ، ( تحفة الأشراف : 2038) ، مسند احمد (6/12) (صحیح)»