Seek for the Sword that was broken is a poem in a dream that both Faramir and Boromir had - Faramir multiple times, and Boromir once.

Seek for the Sword that was broken:
In Imladris it dwells;
There shall be counsels taken
Stronger than Morgul-spells.
There shall be shown a token
That Doom is near at hand,
For Isildur's Bane shall waken,
And the Halfling forth shall stand.

These words were heard in a remote, clear voice, crying out from the West, where there was still some faint light in spite of dark skies.