Strikes continue across Gulf countries amid confusion over status of Strait of Hormuz

Its a religious thing, but since we practiced it for centuries, everyone does it even if they are not religious. Also details may be different based on where people live, but the basics are usually the same. Basically, we mourn the dead the day they die and when we bury them(obviously). Then, we mourn them again on the 3rd day after their death, a week later, and eventually on the 40th day (and sometimes even a year later, if that person was really really close to us such as father or mother. You may also mourn them evey year on the day they died.) I cannot specifically explain what Iranians do in these mourning rites, because it heavily varries from a culture to culture (and iran is a country with huge number of different cultures, such as Persians, lors, kurds, turks, beluch, arabs and many others just living few hundred kilometers from each other. But it usually means meeting the mourning family in their house or a nearby mosque, offering our condolences, sometimes helping them with money to help the mounting family and mourn alongside them for a few hours.) So if you barely knew someone who recently died, you just show up in their funeral. The closer you are, the longer you have to mourn, basically if someone like a father or mother dies, you are expected to wear black clothes for a year or not shave for 40 days. Your best friend? 40 days minimum. a distant family you sometimes talked to? Maybe 7 days at max. Which obviously includes the funeral, third and seventh day. Though you can show up on the 40th day as well, no one stops you from doing that. What's important is, you are not supposed to dance, party, marry or things like that, until the mourning is over to honor the dead and the mourning family. For example if your grandparents died recently, you are not supposed to marry someone or hold a ceremony for at least 40 days. Now, 40th day was important because it was the last day everyone was supposed to mourn the Khamenei, 39th day wasn't that important nor 41th day. That's why making a deal on the 40th day of Khamenei with his killers was offensive to some, to say the least.

Moses spent 40 days and 40 nights wandering

It’s common in a lot of cultures