How can shaving the beard be considered shirk if one's parents command it, especially since there is no explicit divine command in the Qur’an for its obligation, and given that it is considered merely a recommendation for piety that can be achieved through other means, and thus, shaving it does not constitute a disobedience to God’s commands?

The commands of the Prophet, peace and blessings be upon him, are commands from Allah, and Allah has commanded us to obey His Messenger. There are authentic narrations (hadith (definition)) that command the growing of beards and prohibit their shaving, such as the hadith: "Ten are the acts of fitra (natural disposition): trimming the mustache and letting the beard grow." Letting it grow means leaving it untouched, and this is from the Sunnah (definition). So, whoever shaves his beard has gone against the Sunnah and disobeyed Allah and His Messenger. He must beware of tribulation or a painful punishment. The Prophet, peace and blessings be upon him, is a role model for us, and he used to let his beard grow, and it is not authentically reported that he ever trimmed it. The Qur'an also mentions that Harun (Aaron) had a full beard. It is not permissible to obey a created being in disobedience to the Creator, and obedience is only in what is recognized as good.