Ozymandias - S5-E14
Continuity mistake: In the scene where the shootout starts in the previous episode, Walter is handcuffed in the back of the SUV and trying to get to the floorboard to avoid the gunfire, and his glasses eventually fall off. After the gunfight when he is yelling at Jack from the back of the SUV, his glasses are back on his face, which would be hard to do handcuffed.
Chosen answer: It is part of the ritual for la Santa Muerte. It is a sign of humility and sacrifice.
djm