Is bowing in martial arts with the intention of greeting considered major shirk by some scholars, and is it considered as such even if it does not reach the lowest point of bowing? And is one who does not bow, while his opponent bows to him in a manner that may reach the lowest point of bowing, sinful? And is there any religious prohibition in a person jokingly telling his friends, "This was when I was in the days of Jahiliyyah," meaning before his repentance?

Sharia prohibits bowing to a created being, and it is not major shirk (polytheism) if it is merely for greeting and not intended to glorify the created being as God is glorified; however, it is haram (forbidden). If the bowing is intended to glorify the created being as God is glorified, then the one who performs it commits an act of disbelief (kufr), just as if they prostrated to them. As for a slight bend that does not reach the extent of bowing (ruku'), it is disliked (makruh). The minimum extent of bowing (ruku') in a bend is for the palms to reach the knees.