he did not make two prostrations on account of forgetfulness.
Sunan Abi Dawud Book 2, Hadith 624
← Previous Hadith he did not make two prostrations (at the end of prayer) due to forgetfulness until Allah gave him satisfaction about it.

Sunan Abi Dawud Book 2, Hadith 623 Next Hadith → Abu Hurairah reported; The Prophet (ﷺ) offered the noon prayer and he gave the salutation at the end of two rakahs. He was asked. Has the prayer been shortened ? then he offered two rakahs of the prayer and made two prostrations (at the end of it).

Sunan Abi Dawud Book 2, Hadith 625