3 Nephi 1:8

But behold, they did watch steadfastly for that day, and that night, and that day, which shall be as one day, as if there were no night, that they might know that their faith had not been vain.

But they watched steadfastly for that day and night and day which would be as one day without night, so they might know their faith had not been in vain.

But they kept watching faithfully for that promised day and night—the day that would be like one continuous day without darkness—so they’d know their faith hadn’t been wasted.