If a person misses prayers when he is travelling and makes them up when he is at home, he should make them up in shortened form as if he prayed them whilst travelling, according to the more correct opinion, because making u should match the original that was missed. This is the view of the Hanafis and Maalikis, and of the Shaafa‘is in the older madhhab.
See: al-Mawsoo‘ah al-Fiqhiyyah, 27/281
Shaykh Ibn ‘Uthaymeen (may Allah have mercy on him) said in al-Sharh al-Mumti‘ (4/367): A man reached his city then he remembered that he had not prayed Zuhr whilst travelling. So he has to pray it with four rak‘ahs, because it is a prayer that became obligatory for him whilst he was not travelling, so he has to offer it in full. And because shortening the prayer is a concession of travel; once he is no longer travelling then he has to offer it in full.
This is our madhhab; but the more correct view is different, i.e., if he remembers a prayer that should have been offered whilst travelling when he gets home, he should offer it in the shortened form because the Prophet (blessings and peace of Allah be upon him) said: “If a person sleeps and misses a prayer or forgets it, let him offer it when he remembers it,” i.e., let him offer it as it should have been offered. This man remembered that he had not prayed Zuhr when it was two rak‘ahs in his case, so he does not have to offer it in full. End quote.
And he said (4/383): Based on this, there are four possible scenarios with regard to this issue:
1.He remembered a prayer that should have been offered whilst travelling when he was still travelling; so he should offer it in shortened form.
2.He remembered a prayer that should have been offered whilst he was not travelling when he was not travelling; so he should offer it in complete form.
3.He remembered a prayer that should have been offered whilst he was travelling when he was not travelling; he should offer it in shortened form according to the correct opinion.
4.He remembered a prayer that should have been offered whilst he was not travelling when he was travelling; he should offer it in complete form. End quote.
It should be noted that prayer is of great importance and that it is not permissible to delay it until after the time it is due except when joining prayers. If a person sleeps or forgets a prayer, then he should pray it when he wakes up or remembers it, and he is not allowed to delay it. Allah, may He be exalted, says (interpretation of the meaning):
“When you have finished As-Salaah (the congregational prayer), remember Allaah standing, sitting down, and (lying down) on your sides, but when you are free from danger, perform As-Salaah (Iqamat‑as‑Salaah). Verily, As‑Salaah (the prayer) is enjoined on the believers at fixed hours”
“Guard strictly (five obligatory) As‑Salawaat (the prayers) especially the middle Salaah (i.e. the best prayer ‑ ‘Asr). And stand before Allaah with obedience [and do not speak to others during the Salaah (prayers)]”
“Then, there has succeeded them a posterity who have given up As‑Salaah (the prayers) [i.e. made their Salaah (prayers) to be lost, either by not offering them or by not offering them perfectly or by not offering them in their proper fixed times] and have followed lusts. So they will be thrown in Hell”
Ibn Mas‘ood said concerning the word ghayy (translated above as “Hell”): It is a valley in Hell that is very deep and foul.
And Allah, may He be exalted, says (interpretation of the meaning):
“So woe unto those performers of Salaah (prayers) (hypocrites),
5. Those who delay their Salaah (prayer from their stated fixed times)”
[al-Ma‘oon 107:4, 5].
And when the Prophet (blessings and peace of Allah be upon him) was asked: Which deed is dearest to Allah?, he replied: “Prayer offered on time.”
Narrated by al-Bukhaari (527) and Muslim (85).
And he (blessings and peace of Allah be upon him) said: “Whoever gives up ‘Asr prayer, his (good) deeds are rendered invalid.”
Narrated by al-Bukhaari (553).
And he (blessings and peace of Allah be upon him) said: “Do not associate anything with Allaah, even if you are cut and burned. Do not neglect any prescribed prayer deliberately, for whoever neglects it deliberately no longer has the protection of Allaah. And do not drink wine, for it is the key to all evil.” Narrated by Ibn Maajah (4034) and classed as hasan by al-Albaani in Saheeh Ibn Maajah.
We ask Allah to guide us and you and to keep us all steadfast.
And Allah knows best.