And they did not thirst when He led them through the deserts; He caused the waters to flow from the rock for them; He also split the rock, and the waters gushed out. (Isaiah 48:21)
Theodoret of Cyrus (d. 457AD) comments on the event of God bringing water from the rock to quench the thirst of the Israelites sojourning through the desert which St Paul interprets as prefiguring baptism and communion.
Now, I do not want you to be unaware, brethren, that our ancestors were all under the cloud, all passed through the sea, all accepted baptism into Moses in the cloud and in the sea, all ate the same spiritual food and all drank the same spiritual drink (1 Corinthians 10:1-4). These events, he is saying, are a type of ours: the sea resembled the font, the cloud the grace of the Spirit, Moses the priest, the rod the cross, Israel suggesting the baptized, while the Egyptians in pursuit acted as a type of the demons and Pharaoh in person was an image of the devil; after the crossing, you see, the Israelites were freed from the power of the Egyptians, as in a type they also received manna from heaven.
The rock also resembled the Lord’s side: streams sprang up for them unexpectedly, as he brings out more clearly, They drank from a spiritual rock that followed them, remember; the rock was Christ [1 Cor 10:4]. Now his meaning is that for them it was not the rock but divine grace which ensured that the rock unexpectedly gushed floods: if the rock followed them, or water from the rock, how did they need water ever again? (COMMENTARY ON THE LETTERS OF ST PAUL, Vol 1 p 199)
Fraternized 