In Mahabharata, king Virata, out of anger, strikes Yudhishthira's face. Then Draupadi collects the blood due to that act by Virata.
"Vaisampayana continued, 'Saying this, the king inflamed with anger forcibly struck Yudhishthira in the face with a dice, and reproached him angrily, saying, 'Let it not occur again! And having been violently struck, blood began to flow from his nose. But the son of Pritha held it in his hands before it fell on the ground. And the virtuous Yudhishthira then glanced at Draupadi who was standing by his side. Ever obedient to the wishes of her lord, the faultless Draupadi, understanding his meaning, and bringing a golden vessel filled with water, received the blood that flowed from his nose.
Is there any hidden reason behind collecting blood in water? Do scriptures say that blood should be collected in water or blood should not touch the ground?