'Sure' in the Bible

Go to Pharaoh in the morning as he's going down to the water. Stand on the bank of the Nile River and meet him. Be sure to take with you the staff that was turned into a snake.

You are to eat unleavened bread for seven days. On the first day be sure to remove all the leaven from your houses, because any person who eats anything leavened from the first day until the seventh will be cut off from Israel.

Be careful! Be sure to obey him. Don't rebel against him, because he won't forgive your transgression, since my Name is in him.