An abandoned Sunnah:
Answering with “Ahmadullaaha ilayk” (أحمد اللهَ إليك) when someone asks you how you are.
In al-Muwatta’ of Imâm Mâlik ibn Abdullâh ibn Abî Talhah, on the authority of Anas ibn Mâlik ;
That he heard ‘Umar ibn al-Khattâb returning the salaam to someone who gave him the salaam. Then Umar asked the man: “Kayfa anta (how are you)?”
So the man answered:
So Umar said to the man:
“that’s what I wanted to hear from you (i.e. him answering with Ahmadullaaha ilayk).”
Narrated by Imâm al-Bukharî in al-Adab al-Mufrad nr. 473
And in another narration which is Marfû’:
On the authority of ‘Abdullaah Ibn ‘Amr:
The Prophet صلى الله عليه وسلم said to a man:
“Kayfa Asbahta yâ Fulân (how did you wake up O fulaan)?
The man answered:
So the Prophet صلى الله عليه وسلم said:
That is what I wanted (to hear) from you.
As-Silsilah as-Sahîhah 2953