In 2 Kings 6:30, the passage where the two women are arguing about whose son to eat, the king is wearing sackcloth under his regular robes. Why would he do that? What does it mean? Should we be wearing sackcloth today?

The passage reads, "And it came to pass, when the king heard the words of the woman, that he rent his clothes; and he passed by upon the wall, and the people looked, and, behold, he had sackcloth within upon his flesh" (KJV). Sackcloth was worn only in extraordinary circumstances. Here the fate of the people of Samaria is uncertain; they are starving to death. The king seems to want to "get God's attention" through humbling himself.

The word sackcloth comes from the Hebrew saq. In the time of Elisha (2 Kings 6), sackcloth was made from animal hair (goat or camel), and as the name suggests, was a material for making sacks -- for example, to hold grain. (Today it's made from flax or hemp.) It seems to have been worn next to the skin (Job 16:15). Sackcloth made from goat hair, because of its dark (black) color, was highly visible (Rev 6:12); it was meant to be seen (Isaiah 50:3). Perhaps the king was torn between maintaining control (appearing royal) and losing it (throwing himself on God's mercy).

Sackcloth was worn (1) to emphasize personal mourning or national distress (Genesis 37:34; 2 Samuel 3:31; Lamentations 2:10; Esther 4:1; Psalm 30:11; Isaiah 15:3, 22:12; Joel 1:13; Amos 8:10); (2) as a penitential practice (1 Kings 22:27-29; 2 Kings 19:1-2; 1 Chronicles 21:16; Nehemiah 9:1; Psalm 35:13; Jonah 3:5-8; Matthew 11:21; Luke 10:13; and (3) as a means of placating God or others (1 Kings 20:31-32; Jeremiah 4:8, 6:26; Daniel 9:3). Of course sometimes these purposes overlapped.

Some people in the OT were criticized for wearing sackcloth under false pretenses (Isaiah 58:5). Yet God cannot be manipulated. As for today, there's no indication that Christians should be wearing sackcloth, though in the Middle Ages it became fashionable to wear all sorts of uncomfortable garments as a means of mortifying the flesh (the famous hair-skin shirt, or cilice, popular among the monks).