The line quoted by Lee Toric (Donal Logue), "Love alters not with his brief hours and weeks but bears it out even to the edge of doom." is from Sonnet 116 written by William Shakespeare. This is probably what the episode title refers to.
Lee Toric (Donal Logue) tells District Attorney Tyne Patterson (CCH Pounder) that he's staying at the "Pirsig Motel". 'Robert Pirsig' wrote "Zen and the Art of Motorcycle Maintenance".