From Mushin:

The practice of samu was introduced during the Tang Dynasty by Zen Master Baizhang Huaihai into Zen training in Buddhist monasteries. Samu moved them from being solely dependent on wealthy patrons and state sponsorship towards more independent functioning. This encouraged the trainees to take up the daily physical work of farming and maintaining the buildings and grounds as an essential part of practice. This allowed the monasteries to be much more self-sustaining during periods of anti-Buddhist persecution. And had the auspicious side effect of strengthening and extending our own understanding of what we are all about in a life of practice.
Today we continue to bring samu into formal offerings. The spirit of samu turns all our efforts into wholehearted activity. Samu is a way of bringing the whole self to this moment, each moment, in any daily endeavor……washing dishes, paying bills, cleaning, taking care of loved ones, writing reports, and of course maintaining the home for our practice at SJZC. Let’s use Labor Day as a reminder to take up all our responsibilities with the spirit of samu, as glad and wholehearted engagement.