A non-Muslim is asking why Sunnah prayers are offered before the obligatory prayers
Question

                This question has been asked by a non muslim and i do not know how to answer it. muslims believe allah is before everything, why do you pray sunnah before farz? eg fajar, zahur,assar sallah etc.
Praise be to Allah.
    Firstly: 

    We thank you for your interest in matters of your religion, 
    and your keenness to seek goodness for yourself and others. We should point 
    out that discussion with the kuffaar about matters of Islam should only be 
    undertaken by specialists, lest one of them instil doubts in the mind of the 
    Muslim who wants to call them and he becomes confused as to how to answer 
    them. 

    Although we appreciate your sending his question to us and 
    not answering him yourself, we advise you – and those who call others to 
    Allaah in general – not to give the kuffaar the opportunity to debate minor 
    practical issues. Rather discussion with them should be about basic issues 
    from which these minor issues stem and on which they are based. So you 
    should speak about the Oneness of God (Tawheed), proving the Resurrection 
    and the Reckoning, the message of our Prophet Muhammad  (peace and 
    blessings of Allaah be upon him), explaining the beauties of Islam and how 
    it is in accordance with sound human nature and commonsense, refuting shirk, 
    and presenting proof and evidence to support that. 

    There is no reason why you should not reply concerning some 
    of these issues to one whom you know wants to find out the truth; this 
    response may open the door to his entering the religion of Allaah. 

    Secondly: 

    There are some misunderstandings in this non-Muslim’s 
    question, and these mistakes must be addressed before starting to answer in 
    detail. There is no connection between Allaah’s being before all things and 
    the regular Sunnah prayers being offered before the obligatory prayers, 
    because the prescription of doing prayers in this order comes from Allaah. 

    Perhaps he thinks that the naafil and regular Sunnah prayers 
    are offered to the Prophet  (peace and blessings of Allaah be upon him)! 
    Perhaps this is why he is confused about this issue, so he thinks that we 
    draw near to Allaah by offering the regular Sunnah prayers to the Prophet 
     (peace and blessings of Allaah be upon him), and the obligatory prayers 
    to Allaah, may He be exalted. Undoubtedly this is ignorance of the religion 
    of Islam, and it will not be difficult for the Muslim to refute it. 

    Whatever the case, we are the slaves of our Lord, may He be 
    glorified and exalted, and we do what He commands us. The Prophet  
    (peace and blessings of Allaah be upon him) did not enjoin upon the people 
    anything other than that which Allaah commanded him to convey. He is a slave 
    of his Lord just as we are, and the difference between him and us is that 
    Allaah honoured him with the Revelation and Message. Allaah says 
    (interpretation of the meaning):  

    “Say (O Muhammad صلى الله 
    عليه وسلم): ‘I am only a man like you. It has been revealed to me 
    that your Ilaah (God) is One Ilaah (God __ i.e. Allaah)…’”

    [al-Kahf 18:110] 

    “And when Our clear Verses are recited unto them, those 
    who hope not for their Meeting with Us, say: “Bring us a Qur’aan other than 
    this, or change it.” Say (O Muhammad صلى الله 
    عليه وسلم): ‘It is not for me to change it on my own accord; I only 
    follow that which is revealed unto me. Verily, I fear the torment of the 
    Great Day (i.e. the Day of Resurrection) if I were to disobey my Lord’”

    [Yoonus 10:15]. 

    Thirdly: 

     The regular Sunnah prayers offered by the Muslim in a day 
    and a night add up to twelve rak’ahs. Concerning the virtue of these, it is 
    narrated that the one who prays them regularly will have a house built for 
    him in Paradise. This has been discussed in the answer to question no. 1048. 
    They are: two rak'ahs before Fajr, four rak’ahs before Zuhr and two rak’ahs 
    after, two rak’ahs after Maghrib and two rak’ahs after ‘Isha’. 

    Fourthly: 

    The scholars (may Allaah have mercy on them) have mentioned 
    some rulings concerning prayers offered before the obligatory prayer. It is 
    well known that the one who enters the mosque should pray two rak’ahs before 
    sitting down. It is also Sunnah to pray two rak'ahs after doing wudoo’, and 
    also to offer regular Sunnah prayers before some prayers such as Fajr and 
    Zuhr – as stated above. The Prophet  (peace and blessings of Allaah be 
    upon him) also encouraged praying four rak’ahs before ‘Asr, and he 
    prescribed a (Sunnah) prayer before Maghrib, and between the adhaan and 
    iqaamah. All of this is a prescription to offer naafil prayers before the 
    obligatory prayers, and there is great wisdom in that.  

    1.

    Shaykh ‘Abd al-‘Azeez ibn Baaz (may Allaah have mercy on him) 
    said: 

    There are many benefits in these regular Sunnah prayers, and 
    offering them regularly is one of the means of entering Paradise and being 
    saved from Hell, along with offering the obligatory prayers and avoiding 
    haraam things. They are voluntary and not obligatory, but as it says in the 
    hadeeth, the obligatory prayers are perfected by them. They are among the 
    means of attaining Allaah’s love, and doing them is following the example of 
    the Prophet  (peace and blessings of Allaah be upon him). So the 
    believer should offer them regularly and pay attention to them as the 
    Prophet  (peace and blessings of Allaah be upon him) did with the Sunnah 
    prayer of Duha, and tahajjud at night and Witr, so the believer should pay 
    attention to all of that. End quote. 

    Fataawa al-Shaykh Ibn Baaz 
    (11/381). 

    2.

    Shaykh ‘Attiyah Saalim (may Allaah have mercy on him) said: 

    The Muslim should offer the naafil prayer before the 
    obligatory one so as to prepare himself to stand before Allaah when he has 
    the best presence of mind possible. This is a kind of preparation or 
    introduction, because it makes you more alert and focused, and more eager to 
    seek that which is with Allaah. If you start the obligatory prayer 
    straightaway, you may realize that you need some preparation for it. But if 
    you pray the sunnah prayer first, you will be more prepared. Every 
    obligatory prayer – as we said – has a naafil prayer before it. Fajr has two 
    rak’ahs before it, Zuhr has two or four rak'ahs before it, and ‘Asr has four 
    rak’ahs before it. They used to pray two rak’ahs before Maghrib; al-Raawi 
    said: So that if a stranger entered the mosque, and saw people standing 
    behind the pillars, he would think that the people had already prayed 
    Maghrib. It says in the hadeeth: “Pray before Maghrib, pray before Maghrib, 
    pray before Maghrib,” and the third time he said: “for those who wish,” 
    because he did not want the people to take it as a binding Sunnah. And he 
    said: “Between each two calls there is a prayer,” and Maghrib like all other 
    prayers has two calls, namely the adhaan and iqaamah. Similarly before 
    ‘Isha’ there is a naafil prayer, and another after it. End quote. 

    Sharh al-Arba’een al-Nawawiyyah 
    (hadeeth no. 30) 

    3.

    Shaykh Muhammad al-Mukhtaar al-Shanqeeti (may Allaah preserve 
    him) said: 

    The regular Sunnah prayers were prescribed for important 
    reasons. If the worshipper starts with the obligatory prayer straight away, 
    his focus and presence of mind is less than it would be if he had offered 
    the Sunnah prayer before the obligatory prayer, as is the case with Zuhr. At 
    the time of Zuhr people are tired and distracted because of their work and 
    the toughness of seeking to earn a living, so if they start to pray when 
    they have just come from doing business and so on, they will be less focused 
    than if they had started with the Sunnah prayer and then started the 
    obligatory prayer after that. Worship calms one down and makes one more 
    focused, and this is learned from the practice of the Prophet  (peace 
    and blessings of Allaah be upon him). When he wanted to pray qiyaam al-layl, 
    he started with two brief rak’ahs, and they said: Because this initial 
    action prepares one to pray at length, and it helps one to focus properly. 
    The regular Sunnah prayers serve the same purpose. This also happens with 
    the person who comes late to the prayer, or who comes as the iqaamah is 
    being given. When he starts to pray you will not find him having the same 
    focus as if he had come between the adhaan and iqaamah and offered the 
    regular Sunnah prayer and remembered Allaah. One good deed leads to another, 
    so after offering the Sunnah prayer you will find that he is more focused 
    and more calm, and this makes him more able to offer the obligatory prayer 
    with proper presence of mind. This applies if the regular Sunnah prayer 
    comes before the obligatory one. End quote. 

    Sharh Zaad al-Mustaqni’ (Kitaab 
    al-Salaah) 

    And Allaah knows best.