What is the ruling on praying a voluntary prayer while sitting?

Question:
A young man, seventeen years old, says, "I cannot stand for night prayer except while sitting."

Answer:
He prays while sitting. The Prophet (peace and blessings be upon him) used to pray while sitting in the last part of his life (peace and blessings be upon him). It is permissible to pray a voluntary prayer while sitting, but the reward is half. If one has the ability to stand, the reward is half. As for one who is unable, the reward is full.
Q: What if he is able to stand, but only by leaning on something?
A: In that case, he leans on it. In the obligatory prayer, the sick person leans on something and stands.
Q: Is it better to leave it in the case of a voluntary prayer? May Allah reward you.
A: In a voluntary prayer, one should not strain himself. He should pray in the position that is most comfortable for him and in which he has the greatest longing for worship and desire for it.