13 The fire must be kept burning on the altar continuously; it must not go out.

13 The fire shall ever be burning upon the altar; it shall never go out.

13 Remember, the fire must be kept burning on the altar at all times. It must never go out.

13 A fire shall always be burning on the altar; it shall never go out.

13 The fire must be kept burning on the altar all the time; it must not go out.

13 Fire shall be kept burning upon the altar continually; it shall not go out.

13 A continual fire shall be kept burning on the altar: it shall never go out.

13 The fire must always be burning on the altar. It must never go out. 

13 Fire must be kept burning on the altar continually; it must not go out.

13 A perpetual fire shall be kept burning on the altar; it shall not go out.

13 A perpetual fire must be kept burning on the altar; it must not be quenched.

13 The fire must be kept burning on the altar all the time. It must not go out.

13 ‘Fire shall be kept burning continually on the altar; it is not to go out.