"Who ever builds a Masjid for Allah, Allah will Build for him a similar House in Paradise” - Bukhari and Muslim

To spend in the cause of Allah (Subahanahu wa Taala) by way of propagating the Deen of Allah is a charity with high merit and great reward. Some of the common contributions made in this respect are: donations towards the Masjid, which one can do in his own community; however the source of greatest reward is to construct a Mosque. Reward attained through the performance of this kind of good deed affords the continuing of reward even after death.

By providing a place to pray, one receives a reward for each prayer that is made and for any wayfarer who seeks shelter inside. The rewards for the prayer are multiplied each time someone makes salaat. For a large Masjid built as sadaqa jariya for you, your family or community would reap massive rewards in the afterlife for everyone who contributes.

Build for the sake of Allah and he will, insh’Allah, reward you with a palace in paradise.

 

Source - http://abdurrahman.org/zakat/sadaqajaariyah.html