Making demands on your muscles alerts the system to rally all faculties and resources to meet those demands. No demand makes for weakness. Occasional demand, soreness. Steadily increasing demand ensures stronger, larger muscles.
In like manner, we make demands on our faith by presenting it to others, by declaring blessing and truth, and by praying boldly for people. In other words, by taking risks. If this is done persistently, that which fuels faith will sense the demand and rise to it.
Giving out what we have in ever increasing measure places demand, and puts our Source on alert to multiply our supply.