'Altar' in the Bible

That very day, Gad approached David and told him, "Go up and build an altar to the LORD on the threshing floor that belongs to Araunah the Jebusite."

and asked him, "Why has your majesty the king come to his servant?" David replied, "To purchase your threshing floor and to build an altar to the LORD, so the pestilence can be averted from the people."

built an altar to the LORD there, and presented burnt offerings and peace offerings. So the LORD answered David's prayers for the land and the pestilence on Israel was averted.