'Altar' in the Bible

Did I choose him out of all the tribes of Israel to be my priest, to go up to my altar, to burn incense, to wear an ephod before me? Did I give to the house of your father all the offerings of the children of Israel made by fire?

The man of yours, [whom] I shall not cut off from my altar, [shall be] to consume your eyes, and to grieve your heart; and all the increase of your house shall die in the flower of their age.

His return was to Ramah, for there was his house; and there he judged Israel: and he built there an altar to Yahweh.

Saul built an altar to Yahweh. This was the first altar that he built to Yahweh.