preach to the choir
To try to convince someone about something that they already support; to state one's opinion to those who are already most receptive to it. You're preaching to the choir here—we all have kids and understand how busy life can get. Honestly, you're preaching to the choir, but I just don't have any money to donate.
preach to the converted
To try to convince someone about something that they already support; to state one's opinion to those who are already most receptive to it. You're preaching to the converted here—we all have kids and understand how busy life can get. Honestly, you're preaching to the converted, but I just don't have any money to donate.