Rashi on TanakhPsalms 120

A song of ascents which the Levites will recite on the fifteen steps that go down from the Israelites’ court to the Women’s court, and there are fifteen psalms entitled “A song of ascents” (Suc. 5:4, Mid 2:5). And our Rabbis said that David composed them to raise the deep, as is explained in Tractate Succah (53a). And according to the Aggadah (Yerushalmi Sanh. 10:2, 52b), it is to be interpreted: A song for a hundred steps (שיר למאה עולות).

from false lips The arm of those who hunt people with their mouth with wicked accusations.

What can He give you [What can] the Holy One, blessed be He [give you]?

and what can He add to you [What] safeguard and walls? Behold you are placed within two walls.

Sharpened arrows of a mighty man Behold you kill in a distant place like an arrow.

with coals of brooms All coals, when extinguished on the outside, are extinguished on the inside, but these extinguish themselves on the outside but not on the inside (ibid.). Another explanation: What will He give you? What is the Holy One, blessed be He, destined to decree upon you? Arrows of a mighty man with coals of brooms. His arrows from above and Gehinnom from below.

Woe is to me says the congregation of Israel, for I have already suffered in many exiles. Behold I sojourned in Meshech with the sons of Japheth in the kingdom of Persia, Greece, and Meshech.

I am at peace With them.

but when I speak peacefully with them, they come to wage war with me.