Venerable Sariputta addressed the monks thus: "Friends, a monk who wishes to reprove another should first establish five things in himself. What five?
(1) He should consider: 'I will speak at a proper time, not at an improper time;
(2) I will speak truthfully, not falsely;
(3) I will speak gently, not harshly;
(4) I will speak in a beneficial way, not in a harmful way;
(5) I will speak with a mind of loving-kindness, not while harboring hatred.'
A monk who wishes to reprove another should first establish these five things in himself. . . .
"Friends, a person who is reproved should be established in two things: in truth and non-anger. He should reflect: 'If others should reprove me—whether at a proper time or at an improper time; whether about what is true or about what is false; whether gently or harshly; whether in a beneficial way or in a harmful way; whether with a mind of loving-kindness or while harboring hate—I should still be established in two things: in truth and non-anger. If I know: "There is such a quality in me," I tell him: "It exists. This quality is found in me." If I know: "There is no such quality in me," I tell him, "It doesn't exist. This quality isn't found in me." ' "
~The Anguttara Nikaya