The Way to Happiness, by Ibn Qayyim Al-Jawziyya, Ibn Badis
Rejoicing of the heart is one of the greatest and most important things that helps the servant to worship his Lord and Master, as He is pleased. However, this rejoicing has causes that the servant must endeavor to seek out. Once he has succeeded in using these means and Allah grants him joy in his heart, he will be on a light from his Lord. Whoever obtains this will have gained the good of this world and the next. This is why Allah, Purity to Him and Most High be He, says: عَلَىٰ نُورٍ مِّن رَّبِّهِ