As a general rule, one should always assume Scripture writers mean just what they say and that the simplest explanation or interpretation should be considered first.  There is a danger in trying to make everything deep, difficult and “spiritual.”

For instance, baptism (baptizo in the Greek) was a common enough word in New Testament times.  It was not a religious word although it was sometimes used to describe religious ceremonies.  It meant simply to immerse or submerge in some fluid.  “Baptize” was what was done to cucumbers in the making of pickles or to cloth in the process of dyeing.

In some verses, the word is used metaphorically, as in Mark 10:38, “You don’t know what you are asking,” Jesus said. “Can you drink the cup I drink or be baptized with the baptism I am baptized with?” Jesus is speaking of his coming suffering and death and uses these images to illustrate his point.  He will use the same image later in the garden of Gethsemane when he asks that “this cup pass from me.” (Mark 14:36).  Sometimes the word is used to describe the immersion into something other than liquid as when John the Baptist says that Jesus will baptize with the Holy Spirit and fire (Luke 3:16).

But, in Bible times, the most common understanding of the phrase “to be baptized” would have been “to be immersed in water” as in John 3:23,  ^“Now John also was baptizing at Aenon near Salim, because there was plenty of water, and people were coming and being baptized.”

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Strong’s Greek and Hebrew Lexicon

baptizo {bap-tid’-zo}
from a derivative of 911; TDNT – 1:529,92; verb
AV – baptize (76), wash 2, baptist 1, baptized + 2258 1; 80

1) to dip repeatedly, to immerse, to submerge (of vessels sunk)
2) to cleanse by dipping or submerging, to wash, to make clean with water, to wash one’s self, bathe
3) to overwhelm

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“Not to be confused with 911, bapto. The clearest example that shows the meaning of baptizo is a text from the Greek poet and physician Nicander, who lived about 200 B.C. It is a recipe for making pickles and is helpful because it uses both words.  Nicander says that in order to make a pickle, the vegetable should first be ‘dipped’ (bapto) into boiling water and then ‘baptised’ (baptizo) in the vinegar solution. Both verbs concern the immersing of vegetables in a solution. But the first is temporary. The second, the act of baptising the vegetable, produces a permanent change.”

  Bible Study Magazine, James Montgomery Boice, May 1989.