The ruling on praying voluntary prayers while sitting

Question:
If a man enters the mosque, sits, and prays two rak'ahs while sitting on a chair, praying on three pillars, then sits and looks to his right, left, front, and back, and at his face, and he is a man of worship who knows the Book and the Sunnah, yet he deliberately opposes them and does not take heed?

Answer:
This matter requires detail: If it is a voluntary prayer, he may pray it while sitting, and he will receive half the reward. If he prays it while standing, that is better. For all voluntary prayers, he may pray them while sitting and receive half the reward, and if he prays them while standing, he receives the full reward.
And if he is unable to sit on the ground and sits on a chair, he has an excuse if he sits on a chair and bows in the air and prostrates in the air, and he is unable to sit on the ground or prostrate on the ground; he is excused. Allah the Exalted said: [Al-Taghabun: 16].
As for this talk about looking to the right, to the left, above, and behind, this is unreasonable talk. This is the talk of a person who does not understand what he is saying.