Genealogy Challenge

From time to time, as I do editorial passes of the book, I come across little mysteries that remain unsolved and tidbits of tantalizing information that would be nice to expand on. I'm going to start posting these to the blog for all of you to comment on there and research.

The first is about when John Powell and his family first arrived in the Salt Lake valley. The history as written by Ruth Young states:

Arriving in Immigration canyon September 26, 1856, they were met by President Young and several members of the Quorum of Twelve Apostles. They brought watermelons for them. He told them not to eat too much, John said, "Brigham Young was quite sensible."

John's little daughter age 4, who walked all the way, got the large piece of bread and butter she had been promised.

In the afternoon they went down into the valley, camping on the square in the 16th ward, staying from Friday until Monday. Brother Brigham Young told them they had fulfilled a prophecy.

What was the prophecy Brigham Young referred to? Was it a specific one he had uttered and is it recorded anywhere? If it is, where? Or, was it part of the overall prophecy that the Church would grow in the West?

If it helps, here is some more information, quoted from the same account:

June 9, 1856 the Saints left for Salt Lake, pushing and pulling handcarts...John and his family were in Edmund Ellsworth company. John was counselor to the captain of his company...[in late August] the McArthur company was with them going to Laramie.

About 21 September, the company camped at Fort Bridger. Here they stayed all night. "The men killed a beef." Mary says, "This was the first meat since we left the buffalo on the prairies." At Fort Bridger they met Brother Parley P. Pratt. Two men from the fort were on their way to Salt Lake, they asked Captain Ellsworth what message they could take and he told them, "Tell them we haven't a bite of food left in camp." They were completely out of provisions.

A relief party met them with food before they arrived in Salt Lake.