To remain in prayer without obtaining any advantage is not lost time, but a season of great gain, because then we labor without interest, and only for the glory of God. And though at first it may seem as if we labored in vain, it is not so; but it is like what happens to sons who work on their father's estate, and who, though at night they receive not wages for the day's work, yet at the end of the year they receive everything.