What is the authority (sanad) of Imam Ahmad ibn Hanbal's statement regarding the Sunnah of lengthening hair, and does what Sheikh Ibn Uthaymeen said about the Sunnah being to shorten hair contradict the action of the Prophet (peace be upon him)?

Imam Ahmad's evidence that growing hair long is a Sunnah is based on what has been authentically reported: that the Prophet's hair, peace and blessings be upon him, sometimes reached his earlobes, or he would braid it. Imam Ahmad said about growing hair long: "It is a good Sunnah. If we were able to do it, we would have adopted it, but it involves effort and expense."

Based on the statements of scholars, such as Ibn Uthaymeen, growing hair long for men is permissible and subject to people's customs and norms. If the prevailing custom is that those who grow their hair long are a specific group viewed with disdain, then people of honor should not grow it long. However, if the custom is that growing hair long is common among all segments of society, then there is no harm in it.

As for the Prophet's action, peace and blessings be upon him, in growing his hair long, it falls under the category of customs, not acts of worship. Therefore, there is no harm for a Muslim in growing his hair long or shortening it. And whoever grows his hair long out of emulation and love for the Prophet, peace and blessings be upon him, is on a path of goodness.