This excerpt is taken from Sheikh Abu Hamza Abdul Khaliq Siddiqi's book Sahi Fazail-e-Amaal.
Rafi' bin Khadij (may Allah be pleased with him) narrates that I heard the Messenger of Allah (peace be upon him) say:
العامل على الصدقة بالحق كالغازي فى سبيل الله حتى يرجع إلى أهله
"One who collects zakat and sadaqah with honesty for the pleasure of Allah is like a warrior fighting in the cause of Allah until he returns home."
Reference: Sunan Abu Dawood, Book of Kharaaj and Leadership, No: 2936. Sunan Tirmidhi, No: 645. Sunan Ibn Majah, No: 18909. Sahih Ibn Khuzaymah: 4/51.
Ibn Khuzaymah and Allama Albani have declared it authentic.