not incur guilt and die.
“This is to be a lasting ordinance for Aaron and his descendants.

Mark 14:63 The high priest tore his clothes. "Why do we need any more witnesses?" he asked.

It was a symbolic act. It was not necessary that the high priest tore his undergarment and it is forbidden if he was in the Holy Place.
The symbolic point was not necessarily to expose the flesh. If it were, why bothered covering yourself with sackcloth afterward.

2 Kings 19:1 When King Hezekiah heard this, he tore his clothes and put on sackcloth and went into the temple of the LORD.

Esther 4:1 When Mordecai learned of all that had been done, he tore his clothes, put on sackcloth and ashes, and went out into the city, wailing loudly andbitterly.

Joshua 7:6Then Joshua tore his clothes and fell facedown to the ground before the ark of the LORD, remaining there till evening. The elders of Israel did the same, and sprinkled dust on their heads.

1 Kings 21:27 When Ahab heard these words, he tore his clothes, put on sackcloth and fasted. He lay in sackcloth and went around meekly.

Genesis 37:34 Then Jacob tore his clothes, put on sackcloth and mourned for his son many days.

Having said all the above, if a person didn't have any undergarment on, then tearing clothes would expose the flesh. Also, there was nothing to prevent some to tore their immediate undergarment either.

2 Samuel 1:11-12 Then David and all the men with him took hold of their clothes and tore them. They mourned and