Rashi on TanakhPsalms 127

A song of ascents about Solomon This song David recited about his son, Solomon, for he saw through the holy spirit that he [Solomon] was destined to build the Temple, and on that very day, Solomon would marry Pharaoh’s daughter, and concerning this was said (Jer. 32:31): “For this city has aroused My anger and My wrath since the day they built it.” Therefore, he recited this song. My son, why should you build a house and turn away from following the Omnipresent? Since He does not desire it, its workers have toiled at it in vain.

[its] watcher keeps his vigil in vain The watchman watches it in vain.

It is futile for you The craftsmen, who rise early and stay late at their work and sustain themselves with toil and labor, with bread of toil, [i.e.,] of the toil of work.

so will the Lord give The Holy One, blessed be He, [will give] sustenance to him who banishes his sleep from his eyes in order to engage in the Torah.

to one who banishes sleep Heb. לידידו שנא. to one who banishes (מנדד) sleep from his eyes.

Behold, the heritage of the Lord for that man [who banishes sleep from his eyes].

sons These are the disciples whom he sets up, who are to him like sons.

the reward is the fruit of the innards The reward is the fruit of the Torah that is in his heart as it is said (Prov. 22:18): “For it is pleasant that you guard them in your innards.”

Like arrows in the hand of a mighty man with which to battle his enemies.

so are the sons of one’s youth The disciples that a man sets up in his youth.

Praiseworthy is the man who has filled his quiver with those arrows. אשפה is the arrowcase, called cuyvre in Old French.

they will not be ashamed when they talk to the enemies in the gate Torah scholars who defeat one another in halachah and appear as enemies to one another (addendum).