The reward of the one who prays sitting compared to the one who prays standing in voluntary prayers

Question:
He was asked about a woman who has a nightly portion of prayer that she prays, but she is unable to stand in some of the times. It was said to her that the prayer of the one who sits is half the reward of the prayer of the one who stands. Is this correct? He answered: Yes, it is correct. It is narrated from the Prophet (peace and blessings be upon him) that he said: But if his custom is that he prays standing, and he only sits because of his inability, then Allah gives him the reward of the one who stands. This is based on his saying (peace and blessings be upon him): So if he were unable to perform the entire prayer due to illness, Allah would write for him the full reward of it because of his intention and his doing what he was able to do. So how much more so if he is unable to perform its actions?

Answer:
And this is the correct view indicated by the hadith. The one who performs a voluntary prayer sitting, while he is able to stand, is given half the reward. But if he is unable, Allah writes for him a full reward like that of the one who stands, as he said (peace and blessings be upon him): (may Allah have mercy on him). If it is his custom to fast one day and break the fast the next, or to fast on Mondays and Thursdays, or to fast three days of every month, and he travels and leaves off fasting because of the travel, Allah writes for him the reward. Likewise, if it is his custom to pray standing, but when he grows old or is struck by illness he sits, Allah writes for him the reward of the one who prays standing because of the excuse. And he said (peace and blessings be upon him), while on the expedition to Tabuk: And you did not pass through a valley except that they were with you. The excuse held them back. Yes.