وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ إِسْحَاقَ بْنِ عَبْدِ اللَّهِ بْنِ أَبِي طَلْحَةَ، عَنْ أَنَسِ بْنِ مَالِكٍ، أَنَّهُ سَمِعَ عُمَرَ بْنَ الْخَطَّابِ، وَسَلَّمَ، عَلَيْهِ رَجُلٌ فَرَدَّ عَلَيْهِ السَّلاَمَ ثُمَّ سَأَلَ عُمَرُ الرَّجُلَ كَيْفَ أَنْتَ فَقَالَ أَحْمَدُ إِلَيْكَ اللَّهَ ‏.‏ فَقَالَ عُمَرُ ذَلِكَ الَّذِي أَرَدْتُ مِنْكَ ‏.‏

Yahya related to me from Malik from Ishaq ibn Abdullah ibn AbiTalha that Anas ibn Malik heard Umar ibn al-Khattab return thegreeting of a man who greeted him. Then Umar asked the man, "How areyou?" He said, "I praise Allah to you." (Ahmadu ilayka Allah) Umarsaid, "That is what I wanted from you." Translation Not Available

Book Ref: Muwatta Imam Malik Book 53 Hadith 1763
Web Ref:  Muwatta Imam Malik Book 53 Hadith 5