(a) Hamalah bin Abd al-Rahman said: I heard Sayyiduna Umar bin al-Khattab (may Allah be pleased with him) say: There is no prayer without the tashahhud.
(b) It is reported from Sayyiduna Ibn Mas'ud (may Allah be pleased with him): There is no prayer without the tashahhud.
As for what is narrated from Asim bin Damrah from Ali as his own saying, that if he has sat for the length of the tashahhud and then loses his ablution his prayer is complete, it is not sahih (authentic), and Asim bin Damrah is not used as evidence.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2824