And when the day of Pentecost was fully come, they were all with one accord in one place. – Acts 2:1

Have you ever heard of the commencement of the great American revival? A man unknown and obscure, laid it up in his heart to pray that God would bless his country. After praying and wrestling and making the soul-stirring enquiry: “Lord, what wilt thou have me to do? Lord, what wilt thou have me to do?” he hired a room, and put up an announcement that there would be a prayer-meeting held there at such-and-such an hour of the day. He went at the proper hour, and there was not a single person there; he began to pray, and prayed for half an hour alone. One came in at the end of the half-hour, and then two more, and I think he closed with six. The next week came around, and there might have been fifty dropped in at different times; at last the prayer-meeting grew to a hundred, then others began to start prayer-meetings; at last there was scarcely a street in New York that was without a prayer-meeting. Merchants found time to run in, in the middle of the day, to pray. The prayer-meetings became daily ones, lasting for about an hour; petitions and requests were sent up, these were simply asked and offered before God, and the answers came; and many were the happy hearts that stood up and testified that the prayer offered last week had been already fulfilled. Then it was when they were all earnest in prayer, suddenly the Spirit of God fell upon the people, and it was rumored that in a certain village a preacher had been preaching in earnest, and there had been hundreds converted in a week. The matter spread into and through the Northern States-these revivals of religion became universal, and it has been sometimes said that a quarter of a million people were converted to God through the short space of two or three months. Now the same effect was produced in Ballymena and Belfast by the same means. The brother thought that it lay at his heart to pray, and he did pray; then he held a regular prayer-meeting; day after day they met together to entreat the blessing, and fire descended and the work was done. Sinners were converted, not by ones or twos but by hundreds and thousands, and the Lord’s name was greatly magnified by the progress of His gospel. ~ C.H. Spurgeon

https://www.blueletterbible.org/Comm/spurgeon_charles/sermons/0263.cfm