The Prophet (saw) said, "When a man dies, his deeds come to an end except for three things: Sadaqah Jariyah (continuing charity). knowledge which is beneficial or a virtuous descendant who prays for him" [Muslim].

Building a mosque is a wonderful act of Sadaqah Jariyah! The reward for building a mosque is unending, and as long as people are benefiting from the mosque you've helped build then you will continue to receive rewards from Allah (SWT) even in the Hereafter. The benefits of building a mosque are plain as day if you think of the rewards you will receive for every single prayer made in your mosque! A Palace in Jannah