Prayer is the only pillar in Islam that cannot be waived under any circumstances, unless a person is mentally handicapped or unconscious. It has to be performed whether a person is traveling, sick, poor, rich, married, pregnant, old and so on, unlike other pillars (fasting, pilgrimage, and zakah) that can be waived under certain conditions. There is no provision in Islam to miss any Prayers. Even if you are sick and lying in bed in a hospital without being able to move, you have to pray with your eyes. This shows how essential Prayer is and how no one is allowed to downplay its importance.
Sheikh M. S. Al-Munajjid, a prominent Saudi Muslim lecturer and author, states the following: “Whoever misses an obligatory Prayer because of sleep or forgetfulness has to make up for it when he remembers it, because the Prophet (peace and blessings be upon him) said, “Whoever forgets a prayer or sleeps and misses it, let him pray it when he remembers it, for there is no other expiation for it than that” (Al-Bukhari and Muslim). And it was proven that the Prophet (peace and blessings be upon him) made up for the sunnah of Zhuhr after praying `Asr (Al-Bukhari and Muslim).
Al-Nawawi said, “This clearly refers to making up for a missed sunnah Prayer, so it is more appropriate that missed obligatory Prayers should be made up for.” If a Muslim sleeps and misses a Prayer, or he forgets it and does not remember until after `Asr, then he must pray it at that time.”