1 Kings 18:44

"Look, a little cloud no bigger than a person's hand is rising out of the sea." Before going up, Elijah prayed seven times. He did this, in the first place, in order to invite the people who were waiting for the rain, to meditate on the greatness of the grace that they received from their Lord; second, in order to teach them that even if their prayers were not fulfilled [immediately], they should not cease from multiplying their prayers until they were fulfilled at the time appointed by God. And at the seventh time a cloud bringing rain appeared, so that they might know that God had released [them] from the bondage of the famine into the abundance of his mercy in the fourth year, even though he had originally fixed the term to the seventh.

After this blessed Elijah presented himself to the king, "went up to Mount Carmel and put his head between his knees," praying the Lord to send rain on the earth. "And he said to his servant, 'Look toward the sea.' " When the boy reported that he saw nothing at all, he told him, "Go and look seven times." The seventh time he returned and said, " 'I see a little cloud rising out of the sea like a person's foot.' And suddenly the heavens grew dark, and there fell a great rain." For this reason, as we said, Elijah prefigured our Lord and Savior. Elijah prayed and offered sacrifice; Christ offered himself as a spotless sacrifice for the whole world. Elijah prayed for rain to come on the earth; Christ prayed that divine grace might come down into the hearts of humankind. When Elijah told his servant, "Go and look seven times," he signified the sevenfold grace of the Holy Spirit that was to be given to the church. When he declared that he saw a little cloud rising out of the sea, it prefigured the body of Christ, which was to be born in the sea of this world. Therefore, lest anyone doubt, he said that the cloud had the foot of a person who said, "Who do people say the Son of man is?" After three years and six months, rain came down from heaven at the prayer of Elijah, because at the coming of our Lord and Savior the rain of the word of God happily watered the whole world during the three years and six months in which he deigned to preach. Just as at the coming of Elijah all the priests of the idols were killed and destroyed, so at the advent of the true Elijah, our Lord Jesus Christ, the wicked observances of the pagans were destroyed.

After this blessed Elijah presented himself to the king, "went up to Mount Carmel and put his head between his knees," praying the Lord to send rain on the earth. "And he said to his servant, 'Look toward the sea.' " When the boy reported that he saw nothing at all, he told him, "Go and look seven times." The seventh time he returned and said, " 'I see a little cloud rising out of the sea like a person's foot.' And suddenly the heavens grew dark, and there fell a great rain." For this reason, as we said, Elijah prefigured our Lord and Savior. Elijah prayed and offered sacrifice; Christ offered himself as a spotless sacrifice for the whole world. Elijah prayed for rain to come on the earth; Christ prayed that divine grace might come down into the hearts of humankind. When Elijah told his servant, "Go and look seven times," he signified the sevenfold grace of the Holy Spirit that was to be given to the church. When he declared that he saw a little cloud rising out of the sea, it prefigured the body of Christ, which was to be born in the sea of this world. Therefore, lest anyone doubt, he said that the cloud had the foot of a person who said, "Who do people say the Son of man is?" After three years and six months, rain came down from heaven at the prayer of Elijah, because at the coming of our Lord and Savior the rain of the word of God happily watered the whole world during the three years and six months in which he deigned to preach. Just as at the coming of Elijah all the priests of the idols were killed and destroyed, so at the advent of the true Elijah, our Lord Jesus Christ, the wicked observances of the pagans were destroyed. - "Sermon 124.5"