Who says that Isaiah 9:6 does not apply to Christ? Whoever said that is a liar.
JOHN GILL'S COMMENTARY
The mighty God; or "God the mighty One" (r); as some read the words with a comma; but if read together, the sense is the same; Christ is God, truly and properly so; as appears from his name Jehovah, which is peculiar to the most High; from his nature and perfections, being the same with his Father's: from the works performed by him, as those of creation, providence, miracles, redemption, resurrection from the dead, &c.; and from the worship given him, which only belongs to God; also he is called our God, your God, their God, my God, by which epithets those that are not truly God are never called; he is said to be God manifest in the flesh; God over all, blessed for ever; the great God, the living God, the true God, and eternal life; and he is "the mighty One" as appears by the works he did, previous to his incarnation; as the creation of all things out of nothing; the upholding of all things by the word or his power; the management of all the affairs of providence, there being nothing done but what he was concerned in; as the confusion of languages; the burning of Sodom and Gomorrah; bringing the children of Israel out of Egypt; leading and going before them through the Red Sea and wilderness; and bearing and carrying them all the days of old: and also by the works he did when here on earth; as his miracles, called his mighty works; such as healing all manner of diseases by a word speaking, or by touching the person, or by the person touching him, even his garment, or without seeing the person at all, and always without the use of medicines; dispossessing devils out of the bodies of men; power over the elements, as to change water into wine, rebuke the wind and seas, &c.; raising the dead, and even his own body when dead; and, above all, the great work of redemption, by which he appears to be the mighty One indeed; his Father's call of him to it shows it; his undertaking it confirms it; and his actual performance of it puts it out of all doubt; as well as what was then done by him; such as bearing all the sins of his people; engaging with all their enemies; conquering them, and delivering them out of their hands: likewise by what he does now, partly in the conversion of his people; quickening men dead in trespasses and sins; causing dry bones to live; giving spiritual sight to such as were born blind; plucking out of the hands of Satan, and turning from his power to God; which shows him to be stronger than the strong man armed; beginning, carrying on, and finishing the work of faith with power on them; as well as at first making them willing to submit to his righteousness and to be saved by him; and partly in his care of them afterwards; he having the government of them on his shoulders; supplying all their wants; bearing all their burdens; and supporting them under all their afflictions, temptations, and desertions; protecting them from all their enemies; strengthening them to do his will and work; and keeping them from falling totally and finally, and preserving them safe to his everlasting kingdom and glory: moreover, by what he will do hereafter; binding Satan, and confining him for the space of a thousand years; clearing the world of all his and his people's enemies; raising the dead; and judging the world; and destroying wicked men and devils with an everlasting destruction.