Is it permissible to recite the Quran while sitting during the night prayer, then stand for bowing (rukūʿ) and prostration (sujūd)?

There is no harm in performing the supererogatory prayers (Sunan and Nawafil) while sitting, even though standing carries greater reward and merit. This is because the reward for one who stands is double the reward of one who sits, provided there is no valid excuse, as stated in the Hadith: "The prayer of a man sitting is half the prayer." As for one who has an excuse, their reward is not diminished by sitting.