It is narrated from Sayyiduna Abu Mas'ud (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "A prayer in which a man does not keep his back straight in bowing (ruku') and prostration (sujud) is not sufficient."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 14650
It is narrated from Sayyiduna Abu Mas'ud (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "The prayer of anyone (or he said: of a man) in which he does not keep his back straight in bowing and prostration is not sufficient."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 14651
It is narrated from Sayyiduna Uqbah bin Amr (Abu Mas'ud) (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) said: "There is no hope for a prayer in which a man does not keep his back straight in bowing and prostration."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 14652
It is narrated from Sayyiduna Abu Mas'ud (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "A prayer in which a man does not keep his back straight in bowing and prostration is not sufficient," or he said: "when he bows and when he prostrates." Abu Awanah was unsure which words were used.
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 14653
It is narrated from Sayyiduna Abu Mas'ud (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "There is no hope for a prayer in which a man does not keep his back straight in bowing and prostration."
Sufyan said: Al-A'mash said it like this, "there is no hope", meaning "it is not sufficient".
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 14654
It is narrated from Sayyiduna Abu Mas'ud (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "A prayer in which a man does not keep his back straight in bowing and prostration is not sufficient."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 14655
It is narrated from Sayyiduna Uqbah bin Amr (Abu Mas'ud) (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "The prayer of a man who does not keep his back straight for bowing and prostration is not accepted."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 14656