English of Core Text: From here they said: one who is given a cup of blessing to recite and does not recite it has his days shortened, as it is said “I will bless those who bless you.”
On the daf / in context: The discussion concerns the guest who is offered the privilege of leading Birkat HaMazon and declines. Refusal is treated as withholding blessing from the host.
Type of Learning
Custom
What Is Learned
Accepting the opportunity to bless others is itself a source of blessing; declining it carries a cost.