He that laboureth laboureth for himself; for his mouth craveth it of him.
The person who labors, labors for themselves, for their hungry stomach is their motivator. They know that if they do not work, they won’t receive the finances they need to purchase food. So, if they are ever tempted to stop working, their appetite urges them on. The same is true in the spiritual realm, a realization of our spiritual need drives us to the Word of God and prayer.