Hadith ~ Whoever has something good done for him

Usama ibn Zayd reported that the Messenger of Allah, may Allah bless him and grant him peace, said, "Whoever has something good done for him and says to the one who did it, 'May Allah repay your with good,' has made full repayment." [at-Tirmidhi]

Riyad as-Salihin (The Meadows of the Righteous) of Iman Mohieddine Annawawi 631-676. Chapter 252, Hadith 1496.