The minister at Barvas, the Rev James Murray Mackay, had been led to write to Duncan through the prayers of his congregation, and in particular two elderly sisters named Peggy and Christine Smith who had received the God-given assurance that Duncan would be the instrument that God would use to fulfil His purposes on the island.

Duncan was quite unaware of these things and he intended to stay in Lewis for just ten days and then take a rest from his mission work. However, despite his tiredness, he immediately recognised the feeling of spiritual expectation amongst the people who had invited him to Barvas, and after the preaching service on the second evening he was there, the congregation lingered outside the church and were joined by others who had not attended the meeting. At that moment, the voice of a young man was heard praying aloud inside the church, and many were moved to join him as a sense of deep conviction came over the crowd. The church was soon filled with people calling upon God for mercy and praising Him for His goodness, and even when they separated in the early hours of the morning, small groups went on praying in various parts of the village. The powerful awakening which swept through Barvas in the following days was not an isolated event, and although Duncan Campbell's preaching was similarly blessed when services were hastily arranged in villages such as Tarbert, Leurbost and Arnol, the revival was felt throughout the whole of Lewis, to such as extent that he later described it as "a community saturated with God".