A true believer not only serves God by worshiping Him alone, but also the people of various classes by showing kindness towards them!

 

Verses 36-38 of Chapter 4:

Worship Allah and join none with Him in worship, and do good to parents, kinsfolk, orphans, the poor, the neighbor who is near of kin, the neighbor who is a stranger, the companion by your side, the wayfarer (you meet), and those (slaves) whom your right hands possess. Verily, Allah does not like such as are proud and boastful.Those who are stingy and encourage people to be stingy and hide what Allah has bestowed upon them of His bounties. And We have prepared for the disbelievers a disgraceful torment. And (also) those who spend of their wealth to be seen of men, and believe not in Allah and the Last Day, and whoever takes Shaytan as an intimate; then what a dreadful intimate he has!