It is narrated from Sayyiduna Anas (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) said: "The fingers suffice in place of the siwak."
(b) Imam al-Bukhari (may Allah have mercy on him) said: Abd al-Hakam al-Qasmali al-Basri, who narrates from Sayyiduna Anas (may Allah be pleased with him) and Sayyiduna Abu Bakr al-Siddiq (may Allah be pleased with him), is "munkar al-hadith" (his narrations are rejected).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 176
Hadith Gradingمحدثین:منكر
Hadith Takhrij«منكر۔ أخرجه ابن عدي في الكامل 5/334»
Al-Nadr bin Anas narrates from his father (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "The fingers suffice in place of the siwak."
Isa (bin Shu'ayb) alone narrated it with both chains.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 177
It is narrated from al-Nadr bin Anas bin Malik (may Allah have mercy on him) that the Messenger of Allah (peace and blessings be upon him) said: "The fingers suffice in place of the siwak."
This is how I found it in the book of Isa bin Shu'ayb; what is preserved (mahfuz) from the hadith of Ibn al-Muthanna is the narration that follows.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 178
It is narrated from Sayyiduna Anas bin Malik (may Allah be pleased with him) that a man of the Ansar from the tribe of Banu Amr bin Awf said: "O Messenger of Allah, you have greatly encouraged us to use the siwak; is there anything else in its place?" He (peace and blessings be upon him) said: "Your fingers are a siwak at the time of your ablution; rub them over your teeth. Indeed, there is no deed (accepted) for one who has no intention, and there is no reward for one who does not hope for reward from Allah Almighty."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 179
It is narrated from Sayyiduna Anas (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "The finger suffices in place of the siwak."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 180