Psalm 127
v.1
Unless the Lord builds the house, its builders labor in vain. Unless the Lord watches over the city, the watchmen stand guard in vain.
The idea is, that they are entirely dependent on God. No matter what their skill, their strength, their industry may be - all will be in vain unless God shall assist them. They are dependent on Him for life, for health, for strength, for practical wisdom, for a disposition to continue their work, and for success in it. Their work might be destroyed by fire, by a tempest, by an earthquake, or by an irruption of enemies; and for the result, therefore, they are entirely dependent on God.
v.2
In vain you rise early and stay up late, toiling for food to eat - for he grants sleep to those he loves.
See Barnes on Psalm 127 2 Psalm127 v 2.
v.5
Blessed is the man whose quiver is full of them. They will not be put to shame when they contend with their enemies in the gate.
The meaning is, that they would do honor to the family, and gratify the heart of the parent, by their valor in defending their city and home, or in attacking the cities of the enemies of their country. The psalm is designed to inculcate the lesson of dependence on God for success in everything.