References – AN 9.12: With Residue 
“I heard somewhere that the Buddha regretted giving the teaching on the Ten Fetters. Is this true?” Answered by Ajahn Amaro. [Fetters] [Buddha/Biography] // [Great disciples] [Rebirth] [Realms of existence]
Sutta: AN 9.12 Sariputta asks the Buddha whether anyone still subject to rebirth is safe from the lower realms.
Sutta: MN 39: Don’t be content with virtue, etc.