If you have any water that has remained this night in a skin (we would like it), otherwise we would drink directly (from a water source)

Jābir (may Allah be pleased with him) reported that the Messenger of Allah (may Allah's peace and blessings be upon him) entered the house of a man of the Ansār. It is said that he was Abu al-Haytham ibn At-Tayyihān al-Ansāri. The Prophet was accompanied by his Companion Abu Bakr. The Prophet (may Allah's peace and blessings be upon him) asked the Ansāri man if he had any water that had remained overnight in a water skin, and this was in summer.

The wisdom behind that is that the water which remains overnight is cool. If he did not have such water, they would drink water directly with their mouths from a water source, without using a cup or their hand.