If you show mercy to those who are on the earth, He Who is in the heaven will show mercy to you

Bismillahirrahmanirrahim 

Narrated Abdullah ibn Amr ibn al-'As Radi Allahu anhu : The Prophet peace_be_upon_him said: The Compassionate One has mercy on those who are merciful. If you show mercy to those who are on the earth, He Who is in the heaven will show mercy to you. 
Sunan Abu Dawud, Book 41, 4923-Sahih

------------------------------------
Roman translation:
Abdullah ibn Amr ibn al-'As Radi Allahu anhu se rivayat hai ki Rasoollallah SallallahuAlalhi Wasallam ne farmaya Raham karney walo par Rahman bhi raham fermata hai, tum zameen walo par raham karo tum par wo raham karega jo Aasman mein hai(Yani Allah)
Sunan Abu Dawud, Vol 3, 1504-Sahih