Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) narrates that the Prophet (peace and blessings be upon him) said: "Whoever believes in Allah Almighty and the Last Day should speak good or else remain silent."
Al-Bazzar recorded it within a long hadith, and its chain is hasan (good). (Allamah al-Haythami says:) I say: Various chains of this narration have already passed in the Book of Righteousness and Maintaining Ties of Kinship, in the chapter on the rights of the guest.
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الزهد / 18163
Hadith Gradingمحدثین:إسنادہ حسن۔
Hadith Takhrij«اخرجه البزار فى المسند (3574) اخرجه الطبراني فى المعجم الكبير (10843)»