(Isa. 7:3)
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 his 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 (6:13). The son’s presence may have served either of two purposes. It may have been to remind Ahaz of the prophecy that Judah would not be utterly destroyed, or it may have been a reminder that the Lord had prophesied concerning Judah in order 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 inspecting the water supply and deciding how to protect it from the two invading forces. If this was the case, Ahaz’s thinking on these matters would also prepare him to receive the prophecy Isaiah had been sent to deliver.
(Monte S. Nyman, Great Are the Words of Isaiah [Salt Lake City: Bookcraft, 1980], 54.)
The conduit or tunnel that carried water from the city’s only water source, called Gihon Spring, still exists and is located just outside of what used to be the city wall. This made the city very vulnerable in time of siege. The king might have come to this upper pool of Gihon Spring to consider the means by which the city could be defended. But with his heart filled with apostasy and his mind muddled with anxiety over the imminent attack of a huge army from the north, Ahaz would certainly not be in a mood to feel sympathetic to what Isaiah was about to tell him.
(W. Cleon Skousen, Isaiah Speaks to Modern Times [Salt Lake City: Ensign Publishing Co., 1984], 201.)