The transient nature of human existence
Nahj al-Balāgha|Volume 1|Book 3|Chapter 152
١٥٢. وَقَالَ (عليه السلام): لِكُلِّ مُقْبِلٍ إِدْبَارٌ، وَمَا أَدْبَرَ كَأَنْ لَمْ يَكُنْ.
152. Amīr al-mu’minīn, peace be upon him, said: Every comer has to return and after returning it is as though he never existed.