Imam Ali (a.s) was following a funeral and as it was passing along a road, somebody laughed loudly (a sign of discourtesy and lack of manner). Hearing this laugh, Imam Ali (a.s) remarked,
Some of us feel that death is meant for everybody except themselves or it is destined to others and not to themselves or those whom we see dying around us are only travelers going on a journey and will come back to us. It is a sad sight to see that in one moment we commit them to earth and in the next we take hold of the things left by them as if we are going to remain permanently in this world after them. The fact is that we forget sensible advice given to us and become victim of every calamity.
Ref: Nahjul Balagha [ Saying # 122 ]