Q- Is there any Hadith which states that one should take forty steps after eating meals?
Have not come across this in any Hadith.
‘Allamah Ibn Qayyim (rahimahullah) has cited this as the advice of the Arab doctor; Al Harith ibn Kaladah who suggested taking forty steps after partaking of dinner. (Zadul Ma’ad, vol. 4 pg. 374)
Allamah Ibn Qayyim (rahimahullah) has stated that doctors encourage walking after eating and to sleep immediately after eating is quite harmful. Therefore ‘Allamah ibn Qayyim and Hafiz Ibn Hajar (rahimahumallah) have indicated that this a worthy practice to emulate [without attributing it to Nabi sallallahu ‘alayhi wa sallam]. (Zadul Ma’ad, vol. 4 pg. 205 and vol. 2 pg. 370, Nataijul Afkar, pg. 322, Al Faruq Al Hadithah edition and Sharhuz Zurqani ‘Alal Mawahib, vol. 6 pg. 233)
And Allah Ta’ala Knows best.