In the year 1875, when seventy years of age, Mr. Mueller was led to start on his Missionary Tour, and during the next twenty years preached to more than three million people, in forty-two countries of the world.
“On August 8th, 1882,” Mr. Mueller says, “we began our ninth Missionary Tour….we went, by way of Calais and Brussels, to Dusseldorf on the Rhine, where I preached many times six years before. During this visit, I spoke there in public eight times. Regarding my stay at Dusseldorf, for the encouragement of the reader, I relate the following circumstance. During our first visit to that city, in the year 1876, a godly City Missionary came to me one day, greatly tried, because he had six sons, for whose conversion he had been praying many years, and yet they remained unconcerned about their souls, and he desired me to tell him what to do. My reply was, ‘Continue to pray for your sons, and expect an answer to your prayer, and you will have to praise God.’ Now, when after six years I was again in the same city, this dear man came to me and said he was surprised he had not seen before himself what he ought to do, and that he had resolved to take my advice and more earnestly than ever give himself to prayer. Two months after he saw me, five of his six sons were converted within eight days, and have for six years now walked in the ways of the Lord, and he had hope that the sixth son was beginning to be concerned about his state before God. May the Christian reader be encouraged by this, should his prayers not at once be answered; and, instead of ceasing to pray, wait upon God all the more earnestly and perseveringly, and expect answers to his petitions.”
Answers to Prayer, George Mueller, Moody Press, pp. 72-73