'Sign' in the Bible

In those days Hezekiah was sick to the death, and prayed unto the LORD: and he spake unto him, and he gave him a sign.

When the ambassadors of Babylon’s rulers were sent to him to inquire about the miraculous sign that happened in the land, God left him to test him and discover what was in his heart.

And the king, hearing the words of the law, took his robe in his hands, violently parting it as a sign of his grief.