What is the interpretation of the phrase "without speaking to himself" mentioned in the hadith about ablution (then he prays two rak'ahs without speaking to himself in them), and does it mean waswasah (whisperings/satanic insinuations)? If so, does the one who experiences waswasah during prayer lose the reward?

The hadith referred to is that of 'Uthman (may Allah be pleased with him) concerning the description of ablution (wudu'), which is the Prophet's (peace and blessings be upon him) saying: "Whoever performs ablution like this ablution of mine, then prays two units of prayer (rak'atan) in which he does not speak to himself, his past sins will be forgiven." The meaning of "he does not speak to himself" is: he does not succumb to the worldly thoughts that occur to him or anything unrelated to prayer. If a thought occurs to him but he immediately dismisses it, he is forgiven and is not considered to have spoken to himself, because this is not of his doing. And this Ummah has been forgiven for fleeting thoughts that occur but do not settle.