This paper shows the causal relationship between mutual religious association and the formation of social ties. We analyze dyadic relationships and show that joint attendance at a religious institution (RI) increases the probability of sharing information with and trusting a peer. We use a novel spatial instrumental variable strategy that combines insights from homestead inheritance institutions with triangular distances between peers and RI locations within villages in Kenya. We find that shared attendance at an RI increases the likelihood of receiving advice from a peer by 30 percentage points, demonstrating the strong impact of weak ties formed through social spaces.