Why Dasvand?
Dasvand - Dasvand (Punjabi: ਦਸਵੰਧ) literally means "a tenth part" and refers the act of donating ten percent of one's harvest, both financial and in the form of time and service such as sewa to the Gurdwara and anywhere else. It falls into Guru Nanak Dev Ji’s concept of Vand Chakko.This was done during the time of Guru Arjun Dev Ji’s and many Sikhs still follow it religiously.
The concept of dasvandh was implicit in Shri Guru Nanak Dev Ji's own line: "ghali khai kichhu hathhu dei, Nanak rahu pachhanahi sei—He alone, O Nanak, knoweth the way who eats out of what he earneth by his honest labour and yet shareth part of it with others" (GG, 1245). The idea of sharing and giving was nourished by the institutions of sangat and langar the Guru had established.