Musnad Ahmad 4282

Translation

✧ The Prophet ﷺ prayed five (units of prayer) with them, then he added an extra unit. Some people started whispering to each other, so they said to him, "O Messenger of Allah! You prayed five (units of prayer) and then added an extra unit." So he performed two prostrations with them and said, "I am only a human being, I forget just as you forget."

Grades by grader

Narrators

1. 1
   ʿAbdullāh b. Masʿūd

   One of the earliest and foremost (al-sābiqūn al-awwalūn), and one of the leading scholars among the Companions; his virtues are manyd. 28 AH, or 32 AH, 33 AH
   عَبْدُ اللهِ بْنُ مَسْعُودٍمن السابقين الأولين ، ومن كبار العلماء من الصحابة ، مناقبه جمة
   عن
2. 2
   ʿAlqamah b. Qays al-Nakhaʿī

   Trustworthy (thiqah), firm (thabt), jurist, devout worshipperd. 61 AH, or 62 AH, or 65 AH, or 72 AH, or 73 AH, also said: 63 AH
   عَلْقَمَةَثقة ثبت فقيه عابد
   عن
3. 3
   Ibrāhīm al-Nakhaʿī

   Trustworthy (thiqah), except that he often narrates with omission of the Companion (irsāl).d. 94 AH, or 95 AH, or 96 AH
   إِبْرَاهِيمَثقة إلا أنه يرسل كثيرا
   عن
4. 4
   al-Ḥasan b. ʿUbaydillāh

   trustworthy (thiqah), excellent (fāḍil)d. 139 AH, also said: 142 AH
   الْحَسَنَ بْنَ عُبَيْدِ اللهِثقة فاضل
   سمعت
5. 5
   ʿAbdullāh b. Idrīs

   Trustworthy (thiqah), a jurist (faqīh), devout (ʿābid)d. 191 AH, or 192 AH
   ابْنُ إِدْرِيسَثقة . فقيه عابد
   حدثنا
6. 6
   Aḥmad b. Ḥanbal

   Trustworthy (thiqah), a memorizer (ḥāfiẓ), a jurist (faqīh), an authority (ḥujjah).d. 241 AH, Abū Umayyah Muḥammad b. Ibrāhīm al-Ṭarsūsī said: 242 AH, and no one followed him in his view
   أحمد بن حنبلثقة حافظ فقيه حجة

Who each narrator was and how reliable, from hdith.com

Latin names and English verdicts with a dotted underline are machine translations, not reviewed.