He forgot and said Allaahu akbar instead of Sami’aAllaahu liman hamidah
Question

                A man said Allaahu akbar instead of Sami’a Allaahu liman hamidah when standing up after bowing. What should he do?.
Praise be to Allah.Saying Sami’a Allaahu liman 
    hamidah, for both the imam and the one who is praying alone, is one of the 
    obligatory parts of prayer, according to the correct opinion, as was stated 
    in the answer to question no. 43574. 
The one who forgets to say 
    that and does not say anything, or says Allaahu akbar instead of that, and 
    remembers whilst he is still praying, should do the two prostrations of 
    forgetfulness before saying the salaam. 
The basic principle is that 
    the one who forgets an obligatory part of prayer or says a prescribed phrase 
    – such as Allaahu akbar – in the wrong place, should do the prostration of 
    forgetfulness. 
It says in Daleel 
    al-Taalib: The prostration of forgetfulness is required if one adds a 
    bow or prostration or standing or sitting, even if it is as long as the 
    sitting between the two prostrations, or he says the salaam before 
    completing the prayer, or he makes a mistake in recitation that alters the 
    meaning, or he omits an obligatory part. End quote. 
And Allaah knows best.