mourners' bench

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A bench for mourners or repentant sinners placed at the front in a revival meeting.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A bench, seat, rail, pew, etc. set aside for mourners and repentant sinners that is usually found at the front of a revival meeting or southern evangelical church.