I have heard that on one occasion the Blessed One was staying at Rajagaha in the Bamboo Grove, the Squirrels' Sanctuary. Then Vassakara the brahman, the minister to the king of Magadha , approached the Blessed One and, on arrival, exchanged courteous greetings with him. After an exchange of friendly greetings & courtesies, he sat to one side. As he was sitting there he said to the Blessed One: "I am of the view, of the opinion, that when anyone speaks of what he has seen, [saying,] 'Thus have I seen,' there is no fault in that. When anyone speaks of what he has heard, [saying,] 'Thus have I heard,' there is no fault in that. When anyone speaks of what he has sensed, [saying,] 'Thus have I sensed,' there is no fault in that. When anyone speaks of what he has cognized, [saying,] 'Thus have I cognized,' there is no fault in that."
[The Blessed One responded:] "I do not say, brahman, that everything that has been seen should be spoken about. Nor do I say that everything that has been seen should not be spoken about. I do not say that everything that has been heard... everything that has been sensed... everything that has been cognized should be spoken about. Nor do I say that everything that has been cognized should not be spoken about.
"When, for one who speaks of what has been seen, unskillful mental qualities increase and skillful mental qualities decrease, then that sort of thing should not be spoken about. But when, for one who speaks of what has been seen, unskillful mental qualities decrease and skillful mental qualities increase, then that sort of thing should be spoken about.
"When, for one who speaks of what has been heard... what has been sensed... what has been cognized, unskillful mental qualities increase and skillful mental qualities decrease, then that sort of thing should not be spoken about. But when, for one who speaks of what has been cognized, unskillful mental qualities decrease and skillful mental qualities increase, then that sort of thing should be spoken about."
Then Vassakara the brahman, delighting & rejoicing in the Blessed One's words, got up from his seat and left.
See also: MN 58 .