What is the wisdom behind shortening the hair by a fingertip after completing Umrah, and has a Hadith been narrated regarding this, and is a specific place or time stipulated for shortening it?

The Holy Quran is the word of Allah, and Allah Almighty has stated that He has taken it upon Himself to preserve it, saying: "Indeed, it is We who sent down the Dhikr (the Quran) and indeed, We will be its guardian." (Al-Hijr: 9). Therefore, not a single letter can be added to it or removed from it, because Allah has taken it upon Himself to preserve it from any alteration.