put/turn/send somebody out to grass
put out to grass
Also, put out to pasture. Cause to retire, as in With mandatory retirement they put you out to grass at age 65, or She's not all that busy now that she's been put out to pasture. These idioms refer to farm animals sent to graze when they are no longer useful for other work.
put/turn/send somebody out to ˈgrass(informal, humorous) force somebody to stop doing their job, especially because they are old: Old Harry doesn’t seem able to remember anything nowadays. Isn’t it time he was put out to grass?
This expression refers to old farm horses or other animals, which no longer work and stay in the fields all day.