The Lord’s commandment for Isaiah to take his son Shearjashub with him to meet Ahaz is apparently purposeful. A marginal note in the KJV shows the meaning of the son’s name to be “The remnant shall return.” This meaning comes from the prophecy given by the Lord to Isaiah at the time of his call “yet there shall be a tenth, and they shall return” (2 Nephi 16:13). The son’s presence may have been to remind Ahaz of the prophecy that Judah would not be utterly destroyed, or it may have been to prepare Ahaz for the prophecy which Isaiah was to deliver.
Their meeting at the “upper pool” may have not been coincidental either. Many biblical scholars have suggested that Ahaz was there to inspect the water supply (just outside the city) and deciding how to protect it from the two invading forces. If this were the case, Ahaz thinking on these matters would also prepare him to receive the prophecy that Isaiah had been sent to deliver.
The designation of the two kings as “the two tails of these smoking firebrands” (v. 4) also carries meaning. A firebrand was a torch. The description of these two kings as tails that are smoking indicates that their strength had been spent, as a torch smokes only when it is burned out.