3 Nephi 21:7

and when these things come to pass, that thy seed shall begin to know these things, it shall be a sign unto them, that they may know that the work of the Father hath already commenced unto the fulfilling of the covenant which he hath made unto the people which are of the house of Israel.

When these things happen and your children start to know these things, it will be a sign to them. It will show them that the Father has already started to keep the promise he made to the people from the house of Israel.

And when these things happen—when your descendants begin to understand them—it will be a sign that the Father has already started fulfilling the covenant he made with the house of Israel.