Q:

Wa `alaykum As-Salamu waRahmatullahi wa Barakatuh.

Assalamu'alaikum wa rahmatullahi wa barakatuhu.We know from childhood that if we don't do the sunnah things its not a sin on us.

I know from a hadith that disobeying prophet Muhammad ﷺ is disobeying Allah and obeying him ﷺ is obeying Allah.The hadith is:

Narrated Abu Huraira:

Allah's Messenger (ﷺ) said, “Whoever obeys me, obeys Allah, and whoever disobeys me, disobeys Allah, and whoever obeys the ruler I appoint, obeys me, and whoever disobeys him, disobeys me.”

Reference : Sahih al-Bukhari 7137

In-book reference : Book 93, Hadith 1

USC-MSA web (English) reference : Vol. 9, Book 89, Hadith 251

  (deprecated numbering scheme)

There is another hadith also:

It was narrated from Abu Hurairah that the Messenger of Allah (ﷺ) said:

“Whoever obeys me, obeys Allah, And whoever disobeys me, disobeys Allah. Whoever obeys the ruler, obeys me, and whoever disobeys the ruler, disobeys me.”

Grade : Sahih (Darussalam)

Sunnah.com reference : Book 24, Hadith 107

English reference : Vol. 4, Book 24, Hadith 2859

Arabic reference : Book 24, Hadith 2969

This hadith is in Sunan Ibn Majah and it is in the book of the sunnah.

(Source:Sunnah.com)

But there is a hadith:

'Aishah (May Allah be pleased with her) said:

I heard the Messenger of Allah (ﷺ) saying, “No Salat (prayer) should be performed when the food has been served, nor should it be performed when a person is in need of relieving himself.”

[Muslim].

Reference : Riyad as-Salihin 1753

In-book reference : Book 17, Hadith 243

(Source:Sunnah.com)

But when we pray salah when we need to relieve ourself or when food is being served we know that it's not a sin to do so but the salah gets makruh due to it.But why is it not a sin to do so as it's disobeying prophet Muhammad ﷺ?

A:

Wa `alaykum As-Salamu waRahmatullahi wa Barakatuh.

Obedience to the Messenger of Allah is mandatory on us in all of his orders. So, if we know something to be a firm order of the Messenger of Allah to be applied to us all, then we ought to comply with it if we can. If, however, it is only a recommendation, then we have a choice. Likewise, some matters do not concern religion; instead, they belong to purely worldly affairs. We are not bound to follow him in them.

That is why the scholars have distinguished between prescriptive or normative orders or customs of the Prophet (peace be upon him) and those merely customary and have not related to religion. The Prophet himself told us, “You know better about your worldly matters.”  (Muslim)

As for purely normative or religious matters, once we know it is a Prophet’s firm order, we ought to comply with them. The Prophet said, “If I order you something, then do it as best as you can; if I forbid you of something, abstain from it totally; if I am silent of something, consider it as excused.”  (Ibn Hibban)

Almighty Allah knows best.