What is the difference between farah (joy/elation) and sa'adah (happiness/felicity), especially since farah is mentioned in Surah Al-Qasas as something forbidden: "Do not exult, for Allah does not love the exultant" (28:76), while sa'adah is mentioned in the noble Hadith as a matter of choice and preference?

Joy is the opposite of sorrow; it is the expansion of the chest with a fleeting pleasure. As for happiness, it is the opposite of wretchedness and indicates goodness and delight.

Joy is mentioned in the Holy Qur’an, both praised and condemned. The praised joy is that of the Qur’an and Allah’s victory, while the condemned joy is that which distracts and causes one to forget their shortcomings.

As for happiness, it is mentioned in the Qur’an only in Surah Hud, to indicate the state of the people of Paradise and their salvation from Hellfire. What is meant by it is entering Paradise and being saved from Hellfire.

In the noble Hadith, happiness and wretchedness refer to a person’s destiny in the Hereafter. The happy one is he whom Allah guides to perform the deeds of the people of happiness and seals his life with them. And if he performs the deeds of the people of wretchedness, mercy overtakes him, and he repents to Allah.