– اَللَّهُمَّ اغْفِرْ لِيْ ذَنْمبِيْ خَطَئِيْ وَ عَمَدِيْ
Allaahummagh-fir lii dhambii khata’ii wa ‘amadii. (‘Uthman ibn Abil-‘Aas. Musnad Ahmad #17229)
O Allah, forgive my sins, both unintentional and intentional.
While intentional sins are certainly more serious, those committed unintentionally and carelessly are also nothing to be relaxed about. When on one occasion an exchange between the Companions resulted in the raising of their voices in the presence of the Prophet (sallallahu alayhi wa sallem), Allah Ta’aala warned them that such acts could destroy their good deeds, without their even realizing it (Al-Hujuraat, 49:1). Similarly a hadith points out that sometimes a person utters a word carelessly and does not think much about it but it earns for him the wrath of Allah until the Day of Judgment.
(Source: Khalid Baig’s commentary to du’aa #46 in the Accepted Whispers: Munajat-e-Maqbul)