Standing (qiyam)

In an obligatory prayer, the one who is able must stand, from the opening takbir through the recitation. Allah says, ﴿حَافِظُوا عَلَى الصَّلَوَاتِ وَالصَّلَاةِ الْوُسْطَىٰ وَقُومُوا لِلَّهِ قَانِتِينَ﴾ (“Guard the prayers, and the middle prayer, and stand before Allah in devotion.”)

Standing is required only of the one who can do it. 'Imran ibn Husayn, who suffered from an illness, asked the Prophet ﷺ about his prayer, and he told him: pray standing; if you cannot, then sitting; and if you cannot, then lying on your side. The prayer is never dropped, only made easier.

In voluntary prayers a person may sit even when able to stand, though the reward of standing is greater.