Uddaka taught him the doctrine which had been realised and proclaimed by his father Rāma, which was the attainment of the state of "neither-consciousness-nor-unconsciousness" (corresponding to the fourth Jhāna).
The Buddha evidently had a high regard for Uddaka-Rāmaputta, for after the Enlightenment, when looking for someone to whom the Dhamma might be preached, und who was capable of realising its import at once, his thoughts turned to Uddaka, but Uddaka was already dead (Vin.i.7).
In the Vassakāra Sutta of the Anguttara Nikāya (ii.180) it is erwähnt that König Eleyya, together with his bodyguard, Yamaka, Moggalla and others, were followers of Rāmaputta and that they held him in great esteem.
In the Samyutta Nikāya (iv.83f) the Buddha says that Uddaka claimed to be "versed in lore and to have conquered everything, digging out the root of Ill," though he had no justification for such a claim.
Again, in the Pāsādika Sutta (D.iii.126-7), the Buddha tells Cunda that when Uddaka said "seeing, he seeth not," he had in mind a man who saw the blade of a sharpened razor but not its edge - a low, pagan thing to speak about.