# You yourselves are our letter of recommendation

"You yourselves are like our letter of recommendation" 

# written on our hearts

"which Christ has written on our hearts". Possible meanings are 1) Paul and his coworkers are sure about the Corinthians being their letter of recommendation or 2) Paul and his coworkers care very deeply for the Corinthians. 

# known and read by all people

"that all people can know and read"