Those merciful to people
الرَّاحِمُونَ يَرْحَمُهُمُ الرَّحْمَنُ، ارْحَمُوا مَنْ فِي الْأَرْضِ يَرْحَمْكُمْ مَنْ فِي السَّمَاءِ
Ar-rahimuna yarhamuhumu-r-Rahman. Irhamu man fi-l-ardi yarhamkum man fi-s-sama'.
"The merciful are shown mercy by the Most Merciful. Be merciful to those on earth, and the One in heaven will be merciful to you."
Narrated by Abdullah ibn 'Amr. Jami' at-Tirmidhi 1924 (sahih)
A short reflection
A direct trade. Every act of mercy is a transaction with the One above. Cashiers, waiters, children, animals, all of them are the ticket.