It is a pre-requisite of Salah that a person must have done the ceremonial ablution (wudu) and in case of janabah or menstruation or puerperal discharge must have taken the ceremonial bath. In case one has neglected these pre-conditions without any reason, then Salah would not be valid.

Please see for pre-requisites of Salah:

Discussion 71635 • Reply 71643

In all ibada rituals, the principle is to move down to the closest secondary form (e.g. combining prayers or Tayammum) when there’s usr (unusual hardship).

This is primarily based on Quran 2:185

یُرِیۡدُ اللّٰہُ بِکُمُ الۡیُسۡرَ وَ لَا یُرِیۡدُ بِکُمُ الۡعُسۡرَ

“[This concession is because] God desires ease for you and not discomfort“.

A general ruling can’t be made because the situation with one person may justifiably be a hardship, while with another it might be mere inconvenience. Therefore, the final decision on whether or not a particular situation can be justified as unusual hardship rests with the individual. There is a basic level of harship while performing any ritual (whether it be wuzu, ghusl, Salah etc.), therefore this kind of hardship doesn’t fall within purview of this relaxation. It is unusual hardship which is more than the hardship under normal circumstances, but to be decided by the individual when faced with situations other than sickness, travelling and scarcity of water (because these three conditions have been explicitly described by Quran but if the same illat is found somewhere else i.e. unusual hardship, then the same relaxation would also apply). (Please see for details: Discussion 76447)

In case of Salah:

i) In normal circumstances, all effort must be made to offer Salah within the framework provided by Sharia (time, pre-conditions, procedure etc.).

ii) In case of unusual hardship, the same Salah can be performed in its closest secondary form and/or two Salahs can be combined or even reduced to half depending upon the hardship, for example, if it’s difficult to stand up, one can pray on a specified time while sitting down or in worst case scenario, via hand signs only. And if due to any other compulsion, one cannot find a way to offer Salah on time, then one can offer Salah as soon as the situation gets back to normal.

The primary directive where the above mentioned principle is applied by Quran itself is mentioned in Quran 2:239

فَاِنۡ خِفۡتُمۡ فَرِجَالًا اَوۡ رُکۡبَانًا ۚ فَاِذَاۤ اَمِنۡتُمۡ فَاذۡکُرُوا اللّٰہَ کَمَا عَلَّمَکُمۡ مَّا لَمۡ تَکُوۡنُوۡا تَعۡلَمُوۡنَ

“Then if you fear any danger, pray on foot or while riding, as may be most convenient, but when there is security, remember Allah in the very manner He has taught you, which you knew not“.

Prophet Muhammad (sws) with his ijtihad applied the common factor in fear (i.e. choas, haphazardness, undue difficulty etc) to other similar situatons that show similar signs. Another application of this principle can be seen in Quran 4:102 where procedure for Qasar Salah (Salah with rakahs reduced to half) has been given under leadership of Prophet Muhammad (sws). Quran 4:103 is clear that as soon as situation gets back to normal, then Muslims should offer complete Salah on time:

فَإِذَا قَضَيْتُمُ الصَّلاَةَ فَاذْكُرُواْ اللّهَ قِيَامًا وَقُعُودًا وَعَلَى جُنُوبِكُمْ فَإِذَا اطْمَأْنَنتُمْ فَأَقِيمُواْ الصَّلاَةَ إِنَّ الصَّلاَةَ كَانَتْ عَلَى الْمُؤْمِنِينَ كِتَابًا مَّوْقُوتًا

So when the prayer ends, remember God standing, sitting and lying down [in whatever circumstances you are in]. But when the circumstances become peaceful, offer the full prayer, [and, for this, pray at the appointed times] for the prayer is incumbent on the believers at the appointed times.(Quran 4:103)

Therefore, all such relaxations are subject to the principle of “undue hardship” and any Hadith narration, most famoulsy the one from Ibn-e-Abbas (rta) in Sahih Muslim (https://sunnah.com/muslim:705a AND https://sunnah.com/muslim:705b AND https://sunnah.com/muslim:705d AND https://sunnah.com/muslim:705g AND https://sunnah.com/muslim:705h) which apparently give an impression that this relaxation is not subject to any conditions. But when seen in the framework of Quran and Sunnah as explained above, those ahadith are also subject to the same principle of undue hardship and cannot be accepted unconditionally.

For short comments of Ghamidi Sahab on these narrations of Ibn-e-Abbas (rta):

please refer to the video below from 1:57:18 to 1:59:41

https://www.youtube.com/live/uqa3IcMVdW0?feature=share&t=7038

In case of Wuzu and Ghusl:

i) In normal circumstances, all effort must be made to perform wuzu within the framework provided by Sharia (procedure etc.).

ii) In case of unusual hardship, the same wuzu can be performed through tayammum, it is not necessary to use rock or dust at all costs if they are not available, anything pure can serve the purpose. It is just a symbolic action and can be done on any clean surface. Tayammum can also be done in case the same unusual hardhip is stopping one from taking a ceremonial bath. And if hardship reaches to a level where one is even unable to touch any surface with hands, then merel looking at it and performing Tayammum through signs will also suffice.

Based on the above principles, Masah on socks was allowed by Prophet Muhammad (sws). With Qayas done on Tayammum Directive to wearing of socks in a sense that hands would be wiped over socks, but at the same time, the reality of that directive was also kept in its application, which is unusual hardship and it applies to all exemptions in worship rituals. An additional condition of washing feet at the beginning and then after every twenty four hours and three days in case of a traveller was also put and is based on another Quranic directive 2:173, 6:145 and 16:115 غَیۡرَ بَاغٍ وَّ لَا عَادٍ(intending neither to desire nor to transgress).

Similarly, if this relaxation of Masah needs to be extended to other body parts like masah on gloves or arms during wuzu etc., then required hardship needs to increase a step further in order to invoke additional relaxations.

Following response of Ghamidi Sahab can be referred to for further details on this matter of masah:

Discussion 31457 • Reply 31474

Discussion 31457 • Reply 62954

Please watch the videos in the following thread for a detailed discussion on how to approach this whole matter from an epistemological perspective:

Discussion 66552

Discussion 80537

Following videos add further insight into this matter:

https://youtu.be/jijQYGkgS2c