Nahj al-Balāgha
Hadith 2159٢٥١. وَقَالَ (عليه السلام): مَرَارَةُ الدُّنْيَا حَلاَوَةُ الْآخِرَةِ، وَحَلاَوَةُ الدُّنْيَا مَرَارَةُ الْآخِرَةِ.
251. Amīr al-mu’minīn, peace be upon him, said: The sourness of this world is the sweetness of the next world while the sweetness of this world is the sourness of the next one.