The Prophet Muhammad (peace be upon him) said:

"The best among men are those who are most useful to others." - (Hadith)

"When a person dies, all his deeds end except three: continuous charity (Sadaka Jariyah), knowledge that benefits others, and a righteous child who prays for him." (Sahih Muslim)

"Whoever builds a mosque for the sake of Allah, for him Allah will build a house in Paradise." (Sahih al-Bukhari and Sahih Muslim)