15 And when he had said these words, he himself also knelt upon the earth; and behold he prayed unto the Father, and the things which he prayed cannot be written, and the multitude did bear record who heard him.I’ve wondered in the past how it is possible to speak things that can’t be written or even imagined. But I think I’m beginning to realize how it happens. When I was a teenager I would hear people talk with great enthusiasm about service and missionary work and the Spirit of God and a number of other things of spiritual significance, and I couldn’t understand what was so great about them. But as I have gained more experience with these things I have become acquainted with the great joy that comes from them. I’ve learned how satisfying service is. I’ve learned how invigorating and exciting missionary work is. I’ve gotten more in tune with the Spirit of the Lord and a number of other things, and now I find that when someone says those words they seem magical to me, because just the words evoke memories of the wonderful feelings I’ve had.
16 And after this manner do they bear record: The eye hath never seen, neither hath the ear heard, before, so great and marvelous things as we saw and heard Jesus speak unto the Father;
17 And no tongue can speak, neither can there be written by any man, neither can the hearts of men conceive so great and marvelous things as we both saw and heard Jesus speak; and no one can conceive of the joy which filled our souls at the time we heard him pray for us unto the Father. (3 Nephi 17:15-17)
So I think that those words Jesus prayed must have been somewhat like icebergs (remember, 10% above the water, 90% submerged where you can’t see it). 90% of the meaning must have been felt.