One of the most amazing miracles recorded in the Bible occurred when Moses smote the rock on Mount Horeb and water came forth, sufficient to satisfy all the multitude there in the wilderness (Exodus 17:6). In describing this great event, the psalmist later sang: "He clave the rocks in the wilderness, and gave them drink as out of the great depths. He brought streams also out of the rock, and caused waters to run down like rivers" (Psalm 78:15-16).
In our text above, Paul indicates that the miracle had great symbolic significance as well. "That Rock was Christ." The Greek word used here for "rock" is petra, the same word used by Christ when He said that "upon this rock I will build my church" (Matthew 16:18). Christ is the one foundation upon which the church is built (1 Corinthians 3:11). He is also symbolized by the "living water," the "well of water springing up into everlasting life" (John 4:10, 14).
The actual rock from which the waters burst forth in the wilderness did not literally "follow them," of course, but "that spiritual Rock" did follow them, for Christ was there with them through all their years of wandering.
The literal water followed them too, keeping them alive for forty years. When Moses struck the rock, God opened a mighty spring "out of the great depths" (Psalm 78:15), evidently tapping a deep pressurized aquifer from which waters emerged to form "streams also out of the rock" (v. 16). These streams flowed continually in the desert for forty years, so the children of Israel could march and camp beside them as long as they were in the wilderness. Christ still today is our spiritual Rock, continually yielding the spiritual waters of everlasting life. HMM http://www.icr.org/article/5996/