Discussion of the verse “So stand firm and straight (on the religion of Islamic Monotheism) as you are commanded”
Question

                Allah, may He be exalted, says (interpretation of the meaning): “So stand firm and straight (on the religion of Islamic Monotheism) as you are commanded”. What is the story behind this verse?
Praise be to Allah.
      Allah, may He be glorified and exalted, said to His Prophet 
      (blessings and peace of Allah be upon him):

    “So stand firm and straight (on the religion of Islamic 
    Monotheism) as you are commanded, you and those (your companions) who turn 
    in repentance (unto Allah) with you, and transgress not (Allah’s legal 
    limits). Verily, He is All-Seer of what you do” 

    [Hood 11:112].

    Ibn Jareer (may Allah have mercy on him) said: 

    Here Allah, may He be exalted, says to His Prophet Muhammad 
    (blessings and peace of Allah be upon him): stand firm and straight as your 
    Lord has commanded, you and those who follow you in that, and call upon Him, 
    as your Lord has commanded, and those who return with you to obedience to 
    Allah and act in accordance with what their Lord has commanded, after they 
    had disbelieved; and do not transgress against His command and do that which 
    He has prohibited to you, for your Lord has knowledge of all the deeds that 
    you do – both deeds of obedience and disobedience – and nothing of that is 
    hidden from Him, for He sees all of it. So fear Allah, O people, lest your 
    Lord look upon you when you are doing something contrary to His command, for 
    He knows all that you do, and He is constantly watching you.

    End quote from Tafseer at-Tabari (15/499) 

    Ibn Katheer (may Allah have mercy on him) said: 

    Here Allah, may He be exalted, instructs His Messenger and 
    His believing slaves to be steadfast and persist in righteousness, for that 
    is one of the greatest means of help towards victory over one’s enemies and 
    going against one’s opponents. And He forbids transgression, which is 
    wrongdoing, for that is a fatal error even if it is against a mushrik. And 
    remember that Allah, may He be exalted, sees all that people do, and He is 
    not unaware of anything, and nothing is hidden from Him.

    End quote from Tafseer Ibn Katheer (4/354)

     This came after Allah, may He be glorified and exalted, had 
    mentioned the situation of those who are blessed and those who are doomed, 
    and after He, may He be exalted, had said, addressing His Prophet (blessings 
    and peace of Allah be upon him):

    “So be not in 
    doubt (O Muhammad (blessings and peace of Allah be upon him)) as to what 
    these (pagans and polytheists) men worship. They worship nothing but what 
    their fathers worshipped before (them). And verily, We shall repay them in 
    full their portion without diminution.

    Indeed, We gave the Book to Moosa (Moses), but differences 
    arose therein, and had it not been for a Word that had gone forth before 
    from your Lord, the case would have been judged between them, and indeed 
    they are in grave doubt concerning it (this Qur’an).

    And verily, to each of them your Lord will repay their works 
    in full. Surely, He is All-Aware of what they do”

    [Hood 11:109-111]. 

    Having spoken of the situation of both parties, and mentioned 
    the disbelief of those who worshipped idols alongside Allah, and that those 
    who differed concerning the Book became divided into factions, Allah then 
    instructed His Prophet Muhammad (blessings and peace of Allah be upon him), 
    and the believers who were with him, to stand firm and straight (on the 
    religion of Islamic Monotheism) as they were commanded, and follow the laws 
    that Allah had prescribed, and to accept the sound beliefs of which Allah 
    had told them, and not to deviate from that to the right or to the left, and 
    to persist in that, and not to transgress by overstepping the limits of 
    righteousness that Allah had set for them.

    End quote from Tafseer as-Sa‘di (p. 390) 

    We did not find any particular story or incident because of 
    which this verse was revealed. But the context of these verses indicates 
    that the meaning of the verse has to do with what comes before it of the 
    description of those who are blessed and those who are doomed, and the state 
    of the mushrikeen and those who differed concerning the Book. So it is an 
    instruction to the Prophet (blessings and peace of Allah be upon him) and 
    those who believed with him, telling them to stand firm and straight, and 
    not to deviate or overstep the mark. Hence it begins with the word fa 
    (translated here as “so”), in the phrase 
    “So stand firm and straight”, 
    which connects it to what comes before it. 

    To sum up the meaning: You – O noble Messenger – know the 
    situation of those who are blessed and the situation of those who are 
    doomed, and We have told you of the situation of the mushrikeen and the 
    situation of those who differed concerning the Book, and We have told you 
    that every accountable person will be requited in full for his deeds. So 
    adhere, you and the believers with you, to the path of adherence to the 
    truth, and persist in that as Allah has commanded you, without being 
    heedless or going to excess, and beware of overstepping the limits of 
    moderation in all your words and deeds; do not be like those who became 
    divided and differed after clear proof had come to them, so that you may be 
    among those who are blessed, and not be among those who are doomed. 

    Therefore, when a man came to the Prophet (blessings and 
    peace of Allah be upon him) and said: O Messenger of Allah, tell me of 
    something in Islam that I shall not ask anyone else about after you. He 
    said: “Say, ‘I believe in Allah,’ then stand firm and straight.”

    Narrated by Ahmad (14991) and at-Tirmidhi (2410); classed as 
    saheeh by al-Albaani in Saheeh at-Tirmidhi 

    And Allah knows best.