Isn't the doctrine of the Trinity supported by Genesis 19:24: "Then the Lord caused to rain upon Sodom and Gomorrah brimstone and fire from the Lord out of heaven?"
It has been alleged by some Christian theologians that there are two divine personalities mentioned in this verse, one on earth, conversing with Abraham, and the other in heaven. The one on earth, it is claimed, rained down fire upon the two cities from the one in heaven.
There is, however, no grammatical basis for such an inference. In accordance with the construction of the Hebrew language, we find that in the first half of the verse, the reader is informed who caused the brimstone and fire to fall upon the two cities. In the second half of the verse he is told for emphasis, not only from whom it came but also from where. The verse emphasizes that it is "from the Lord," in order to leave no doubt as to who is in command of events.
An individual will often speak of himself in the third person instead of using the first person. Examples of this may be seen in the following: Lamech said, "Hear my voice you wives of Lamech" (Genesis 4:23), not "my voice"; similarly David said, "Take with you the servants of your lord" (1 Kings 1:33), and not "my servants"; and Ahasuerus said, ". . . in the name of the king" (Esther 8:8), not "in my name." They are all referring to themselves in the third person not to another personality. Likewise, when God speaks of Himself in the third person He is also not speaking of another personality.
God uses the technique of speaking in the third person about Himself in a number of scriptural contexts. It is a common feature of the Scriptures, when "the Lord" (HaShem) speaks, for the text to repeat the noun rather than make use of a pronoun (e.g. Genesis 18:19; Exodus 3:12, 24:1; Numbers 19:1-2; Zechariah 1:17).
As we can see, the use of "from the Lord" rather than "from Him," in the verse under discussion, conforms to the biblical usage. There is no scriptural reason to assume that two divine personalities are mentioned.