Al-Tabarani recorded it in al-Mu'jam al-Awsat, except that he recorded these words: "Sayyiduna Mu'adh (may Allah be pleased with him) said: 'O Messenger of Allah! Command me to a deed that will make me enter Paradise.' The Prophet (peace and blessings be upon him) said: 'Believe in Allah, and speak good; it will be recorded in your favour. Do not speak evil, or it will be recorded against you.' He asked: 'Will we be taken to account for what we speak?'" After this, the narrator mentioned the hadith as before.
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الزهد / 18159