This seems to be Paul discussing his conversion experience. Prior to his conversion, Paul was a brutal, self-righteous Pharisee that persecuted Christians. In the New Testament, Christ refers to the Pharisees as white-washed sepulchers (referenced here by Dustin with “Kept a close watch on the white wash, disguising the dead bones inside”).
However, Paul radically converted to Christianity when he was blinded on the road to Damascus. Dustin references this when he sings, “But you buried me in the bright light/ Yeah, you held my eyes to the sun till I could see.” After being literally temporarily blinded by a bright light and hearing the voice of God, Paul could “see” his own hypocrisy. Through this experience he realized God’s love.
I think Thrice uses this story to remind the self-righteous among us (Christian and non-Christian alike) to follow God’s command to love all people because none of us are blameless. Without love, we are truly dead inside despite whatever righteous front we put up- white-washed sepulchers “disguising the dead bones inside.”
From the comment section on this page (because whoever wrote it hit the nail on the head, leaving no need for me to even try).