Solemnity of the Saints Peter and Paul: 29th of June.
I love these powerful words of our lord, Jesus Christ:
You are Peter and on this rock I will build my Church.
And the gates of the underworld can never hold out against it.
You are Peter, and I will give you the keys of the kingdom of heaven; whatever you bind on earth will be bound in heaven, and whatever you loose on earth will be loosed in heaven.