At some point you might find yourself outside of SQL Server Management Studio and need to get the contents of a stored procedure. Maybe you want to edit the proc or just list the source in sqlcmd. Either way, SQL Server includes two built-in procedures called "sp_helptext" and "sp_help" that are great resources in cases like this.
Below, I am getting the content of my stored procedure called "InsertNewUser":
USE ProdDB
exec sp_helpText 'InsertNewUser'
USE ProdDB
exec sp_help 'UserTbl'
exec sp_help 'InsertNewUser'