Is it permissible for a worshiper to rest in the middle of the row while people are praying, knowing that this breaks the row?

If a worshipper is unable to stand during an obligatory prayer, it is permissible for him to sit, based on the Prophet's (peace be upon him) saying to Imran ibn Husayn: "Pray standing; if you are unable, then sitting; if you are unable, then on your side." His sitting does not constitute breaking the row. As for voluntary prayers, it is permissible to sit even if one is able to stand, but the reward for one who prays sitting is half the reward of one who prays standing.