None of the people of the Qiblah is declared a disbeliever because of a sin

Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) narrates that the Prophet (peace and blessings be upon him) said: "Hold back from the people of 'La ilaha illallah' (there is no god but Allah), and do not declare them disbelievers because of a sin. Whoever declares the people of 'La ilaha illallah' to be disbelievers is himself closer to disbelief."
Al-Tabarani recorded it in al-Mu'jam al-Kabir; its chain mentions that al-Dahhak bin Humrah narrated it from Ali bin Zayd, and there is disagreement about using the two of them as evidence.

Sayyiduna Abu al-Darda', Sayyiduna Abu Umamah, Sayyiduna Wathilah bin al-Asqa' and Sayyiduna Anas bin Malik (may Allah be pleased with them) relate: Once the Prophet (peace and blessings be upon him) came out to us while we were arguing about a religious matter. The narrator then mentioned the whole hadith, further on in which come these words: "Islam began as something strange, and it will soon return to being strange." The people said: O Messenger of Allah, who are the strangers? The Prophet (peace and blessings be upon him) said: "Those who remain upright when other people become corrupt, and they do not argue about the religion of Allah. Do not declare any of the people of tawhid (monotheism) a disbeliever because of committing a sin."
(Allamah al-Haythami says:) This complete narration will come later.
Al-Tabarani recorded it in al-Mu'jam al-Kabir; its chain contains Kathir bin Marwan, whom Yahya and al-Daraqutni (may Allah have mercy on him) declared a liar.

Sayyiduna Ali (may Allah be pleased with him) and Sayyiduna Jabir (may Allah be pleased with him) narrate that the Prophet (peace and blessings be upon him) said: "Islam is built upon three things: the people who say 'La ilaha illallah' (there is no god but Allah), do not declare them disbelievers because of any sin, and do not bear witness of shirk (associating partners with Allah) against them; knowledge of the divine decree, that its good and its bad are from Allah Almighty; and jihad, which will continue until the Day of Resurrection, from the time Allah Almighty sent Sayyiduna Muhammad (peace and blessings be upon him) until the last band of the Muslims (it will continue); neither the tyranny of a tyrant nor the justice of a just ruler will bring it to an end."
Al-Tabarani recorded it in al-Mu'jam al-Awsat; its chain contains Isma'il bin Yahya al-Taymi, who used to fabricate hadith.

Sayyiduna Abu Sa'id al-Khudri (may Allah be pleased with him) reports this saying of the Prophet (peace and blessings be upon him): "No one will leave faith except by denying that which he entered into."
Al-Tabarani recorded it in al-Mu'jam al-Awsat; its chain contains Isma'il bin Yahya al-Taymi, and he is a fabricator of hadith, as has already been mentioned.

Sayyidah Aishah Siddiqah (may Allah be pleased with her) relates: I heard the Prophet (peace and blessings be upon him) say: "Do not declare anyone of the people of the qiblah a disbeliever because of a sin, even if they commit major sins; pray behind every imam, and wage jihad with every commander."
Al-Tabarani recorded it in al-Mu'jam al-Awsat; its chain contains Ali bin Abi Sarah, and he is da'if (weak) and matruk al-hadith (abandoned in hadith).

Yazid al-Raqashi reports this about Sayyiduna Anas bin Malik (may Allah be pleased with him): I said: O Abu Hamzah, some people bear witness against us of disbelief and shirk (associating partners with Allah). Sayyiduna Anas (may Allah be pleased with him) said: They are the worst of creation and of created beings.
Abu Ya'la recorded it; its chain contains Yazid al-Raqashi, whom most scholars declared da'if (weak), while Abu Ahmad bin Adi declared him thiqah (trustworthy) and said: He has sound narrations from Sayyiduna Anas (may Allah be pleased with him), and I hope there is no harm in him.

Abu Sufyan relates: I questioned Sayyiduna Jabir (may Allah be pleased with him), who was at that time staying in Makkah and had taken lodging among the Banu Fihr. A man asked him: Did you, that is, the Companions (may Allah be pleased with them all), call anyone of the people of the qiblah a mushrik (polytheist)? He replied: I seek refuge in Allah from that! He (that is, Sayyiduna Jabir (may Allah be pleased with him)) was alarmed by this. The man asked: Did you (that is, the Companions) call any of them (that is, the people of the qiblah) a disbeliever? He replied: No.
Abu Ya'la and al-Tabarani in al-Mu'jam al-Kabir recorded it, and its narrators are the narrators of the Sahih.