Be strong and of good courage; for you shall cause this people to inherit the land which I swore to their fathers to give them.
From this passage, therefore, let us learn that we can never be fit for executing difficult and arduous matters unless we exert our utmost endeavors, both because our abilities are weak, and Satan rudely assails us, and there is nothing we are more inclined to than to relax our efforts. (21) But, as many exert their strength to no purpose in making erroneous or desultory attempts, it is added as a true source of fortitude that Joshua shall make it his constant study to observe the Law. By this we are taught that the only way in which we can become truly invincible is by striving to yield a faithful obedience to God. Otherwise it were better to lie indolent, and effeminate than to be hurried on by headlong audacity. 