How can the sayings of scholars—which define contentment (rida) as the absence of pain in the heart from a calamity—be reconciled with the actions of the Messenger of Allah, peace and blessings be upon him, and the state of Jacob, peace be upon him, which indicate the presence of sadness and pain? And are there limits to sadness that permit attaining contentment?

There is no contradiction between the heart's sorrow out of mercy and compassion for a creature, and contentment with Allah's decree and governance. Indeed, the Prophet, peace and blessings be upon him, wept in sorrow over the death of his son Ibrahim, and Jacob, peace be upon him, grieved over Joseph, and the Prophet, peace and blessings be upon him, grieved over the killing of his companions. This is from the perspective of mercy and compassion. Ibn al-Qayyim clarifies that the Prophet's weeping was out of tenderness and mercy for his child, while his heart was filled with contentment with Allah and gratitude towards Him, and his tongue was engaged in His remembrance and praise. Sheikh al-Islam Ibn Taymiyyah mentioned that the Prophet's guidance was the most perfect, because he gave servitude its full due. His heart was expansive enough for contentment with Allah and mercy for the child, so he praised Allah and was content with His decree, and he wept out of mercy and tenderness. This indicates that sorrow from some aspects does not contradict contentment with Allah's destiny and decree.