Praise be to Allah.
The Muslim should maintain the habit of
praying regularly on time, for Allaah praises the believers who, as
He says (interpretation of the meaning):
“And those who guard their Salaah (prayers) well”
If a person has an excuse and he missed a prayer, then he has to make it up, because the Prophet (peace and blessings of Allaah be upon him) said: “Whoever forgets a prayer or sleeps and misses it, the expiation for this sin is to pray it when he remembers it.” (Narrated by Muslim, al-Masaajid wa Mawaadi’ al-Salaah, 1103)
If you miss a prayer, then you have to pray that prayer first, then pray the current prayer; it is not permissible to delay (making up the missed prayer). It is commonly thought among the people that if a man misses a fard prayer, he should make it up with the corresponding fard prayer of the next day, so that if, for example, he missed Fajr on one day he can only pray it with Fajr on the second day. This is wrong, and it goes against the teaching of the Prophet (peace and blessings of Allaah be upon him), in both his words and deeds.
It was narrated that he said: “Whoever forgets a prayer or sleeps and misses it, then let him pray it when he remembers it.” He did not say, let him pray it on the following day when the time for that prayer comes, rather he said, “let him pray it when he remembers it.” With regard to his actions, when he missed a prayer on one of the days of the campaign of al-Khandaq, he prayed it before the current prayer, which indicates that one has to pray the missed prayer and then pray the current prayer. But if he forgets and prays the current prayer before the missed prayer, or he was ignorant and did not know (of the ruling), then he prayer is valid because he has an excuse.
(See Fataawa al-Shaykh Ibn ‘Uthaymeen, vol. 12, p. 222)
The hadeeth about the prayer on the day of al-Khandaq was narrated by al-Nasaa’i from ‘Abd al-Rahmaan ibn Abi Sa’eed from his father, who said: “The mushrikeen kept us busy on the day of al-Khandaq and distracted us from praying Zuhr until the sun set. Then the Messenger of Allaah (peace and blessings of Allaah be upon him) commanded Bilaal to call the iqaamah for Zuhr prayer, and he prayed it, then he called the iqaamah for Asr and he prayed it, then he called the adhaan for Maghrib then he prayed it as he usually prayed it, on time.” (al-Adhaan, 655; classed as saheeh by al-Albaani in Saheeh al-Nasaa’i, no. 638)
The action of the Prophet (peace and blessings of Allaah be upon him) indicates that it is obligatory to pray the missed prayers in the right order. But if there is only enough time left to pray the current prayer, then he should pray the current prayer, then pray the ones that came before it.