The phrase with which Paul introduces his new argument (literally, For I do not want you to be unaware) was a standard way of introducing an exposition. In what follows, Paul will remind the Corinthians of the history of the exodus. He begins by reminding them that the Israelites of old are their fathers.

Not all the Corinthians are Jews, yet all of them are children of Israel through faith (see Romans 11:16–20). It is important that they identify themselves with the Old Testament Israelites because, as Paul will argue, what happened to the Israelites can also happen to them.

The cloud in this verse refers to the pillar of cloud with which God led the Israelites through the desert. In the book of Numbers (Numbers 10:34 and Numbers 14:14) the cloud is said to have been over the Israelites. This explains why Paul describes the Israelites as being under the cloud.

The sea refers to the Red Sea, which was miraculously parted for the Israelites to pass through (Exodus 14:1–31).