Musnad Ahmed: Hadith 4133

Verily Muhammad (ﷺ) was taught how to start all acts of goodness and all acts of goodness and how to conclude all acts of goodness. And he said: "When you sit after each two rak'ahs, say: 'All compliments, prayers and pure words are due to Allah, Peace be upon you, O Prophet, and the mercy of Allah and His blessings. Peace be upon us, and upon the righteous slaves of Allah. I bear witness that there is no god but Allah, and I bear witness that Muhammad is His slave and Messenger. Then let one of you choose whatever supplication he likes and call upon his Lord, may He be glorified and exalted, with it.” And verily Muhammad (ﷺ) said: “Shall I not tell you what calumny is?” He said: "It is malicious gossip that is spread among people.” And verily Muhammad (ﷺ) said: "A man may tell the truth until he is recorded as a speaker of truth, and he may lie until he is recorded as a liar."