Shaykh Ahmad bin Yahyaa an-Najmee was asked :

"What is the ruling on saying “shukran” to the one who rendered goodness to a person?"

He replied:

"Whoever did that has abandoned that which is more superior, which is the saying, “Jazaak Allaahu khayran” (may Allah reward you with good)."

And in Allah lies success.

 
[Taken from: Fath Rabbil-Wadood Fil-Fataawaa war-Rasaa’il war-Rudood 1/68, no. 30]

Translated by: Abu Iyaad Amjad Rafiq