The Places of the Prostration for Forgetfulness

Question:
The questioner, Abd al-Hadi, asks: Regarding the prostration for forgetfulness, is it obligatory for us to perform the prostration for forgetfulness for all errors in the prayer, even if it is forgetting the first tashahhud or forgetting one of the two prostrations?

Answer:
The prostration for forgetfulness is prescribed for several matters. First, adding to the prayer by mistake, such as praying a fifth rak'ah in a four-rak'ah prayer or a third rak'ah in the Fajr prayer by mistake. If one adds to the prayer by mistake, he prostrates for forgetfulness. Or it is for a deficiency, such as if one stands up from the first tashahhud, or leaves out saying "O Allah, forgive me" between the two prostrations, or "Glory be to my Lord, the Most High" in the ruku', or "Glory be to my Lord, the Most High" in the sujud. If one leaves out an obligatory part of the prayer by mistake, he prostrates; it is obligatory for him to prostrate for forgetfulness. This is prostration for a deficiency.
The third is prostration for doubt. If one doubts about the number of rak'ahs, he builds on the lesser number because that is what he is certain of, and he performs what he doubted about, and he also prostrates for forgetfulness. Yes.

The presenter:
May Allah reward you with good,