The literal translation of Misak vechem dhanvon; zhuzak vechem ravon
This proverb isn’t to be taken literally or for its face value. The general message of the proverb is: there is a time for everything — there is a time when you need to hurry and there is a time when you would rather be tardy.
The Mass and the war are just examples of situations that call for different types of responses. The reason for selecting the Mass as an instance that demands punctuality is the belief that if one is late for Mass, one’s attendance at the Mass isn’t valid, whereas in the case of war, since going to war is in itself an undesirable thing but is thrust upon you, you might as well take it easy and go about the business with as much delay as you possibly can.