On the nature of the work we do take family names to the temple, Boyd K. Packer said,

“Now, there are those who scoff at the idea of vicarious ordinances performed for the salvation of souls. They think it all to be very strange.

No thinking Christian should be surprised at such a doctrine. Was not the sacrifice of Christ a vicarious offering for and in behalf of all mankind? The very Atonement was wrought vicariously.

The Lord did for us what we could not do for ourselves. Is it not Christlike for us to perform in the temples ordinances for and in behalf of those who cannot do them for themselves?”

“Covenants”
April 1987 General Conference