The one baptism of Ephesians 4:5 is not the baptism unto Moses:  “Moreover, brethren, I do not want you to be unaware that all our fathers were under the cloud, all passed through the sea, all were baptized into Moses in the cloud and in the sea,…”  I Corinthians 10:1,2

The background of this passage is an event recorded in Exodus 14:5-30, namely, the deliverance of the children of Israel from the Egyptians at the crossing of the Red Sea. It was described as a “baptism” because they were encompassed by the cloud above them and the water heaped up on both sides (see Exodus 14:20-22). This “baptism” was, for them, the moment of their deliverance from the bondage of Egypt (typical of great commission baptism wherein sinners are delivered from the bondage of sin (see 1 Corinthians 10:11; Romans 6:17-18). However, it must be remembered that Israel’s “baptism” was an historical event that happened but once. Consequently, the baptism unto Moses cannot be the one baptism that would last to the end of the world, for what happened to Israel at the Red Sea was peculiar to them and was not universal in its application. 

Therefore, the baptism unto Moses cannot be the “one baptism” of Ephesians 4:5 which is in force today.