What is the ruling on offering the regular Sunnah prayer that is usually offered after the obligatory prayer, before the obligatory prayer?
Question

                Is it permissible for someone to pray the 2 unit of sunnah of esha salaah beforehand of the obligatory prayer ? If someone prayed it without knowledge about the ruling, what is the stand ?
Praise be to Allah.
      The regular Sunnah prayers are of two types: 

    1.The Sunnah prayers that are 
    offered before the obligatory prayer. They are: two rak‘ahs before Fajr and 
    four rak‘ahs with two tasleems (i.e., offered two by two) before Zuhr.

    The time for this type of Sunnah prayer begins when the time 
    for that prayer begins, and lasts until one begins to offer the obligatory 
    prayer. 

    2.The Sunnah prayers that are 
    offered after the obligatory prayer. They are: two rak‘ahs after Maghrib, 
    two rak‘ahs after ‘Isha’ and two rak‘ahs after Zuhr.

    The time for this type of Sunnah prayer begins when the 
    obligatory prayer is over and lasts until the end of the time for that 
    prayer. 

    Ibn Qudaamah (may Allah have mercy on him) said: With regard 
    to every Sunnah prayer that is offered before the obligatory prayer, its 
    time lasts from the beginning of the time for that prayer until the start of 
    the obligatory prayer. With regard to every Sunnah prayer that is offered 
    after the obligatory prayer, its time lasts from when that prayer is 
    finished until the end of that time.

    End quote from al-Mughni, 1/436 

    It says in al-Mawsoo‘ah al-Fiqhiyyah (25/281-282): The 
    regular Sunnah prayers are connected to the obligatory prayers; some of them 
    are offered before the obligatory prayer, such as the Sunnah prayer of Fajr 
    and the Sunnah prayer that comes before Zuhr. And some of them are offered 
    after the obligatory prayer, such as the Sunnah prayer that comes after 
    Zuhr, the Sunnah prayers of Maghrib and ‘Isha’, Witr, and qiyaam in Ramadan 
    (i.e., Taraweeh).

    With regard to whatever of these Sunnah prayers come before 
    the obligatory prayer, the time for them begins when the time for the 
    obligatory prayer begins, and ends when the iqaamah for the obligatory 
    prayer is given, if that iqaamah is given in a group or congregation 
    (jamaa‘ah), because once the iqaamah is given for prayer, there is no prayer 
    except the prescribed obligatory prayer. But if an individual is going to 
    offer the prayer on his own, the time for the Sunnah prayer lasts until he 
    begins the obligatory prayer. 

    With regard to the Sunnah prayers that come after the 
    obligatory prayer, such as the Sunnah prayer that comes after Zuhr and the 
    Sunnah prayers of Maghrib and ‘Isha’, the time for each of them begins when 
    the obligatory prayer has been completed and lasts until the time of the 
    obligatory prayer ends and the time for the next prayer begins.

    End quote. 

    Based on the above, if a person offers the Sunnah prayer that 
    should be offered after ‘Isha’ before he prays ‘Isha’, it is as if he has 
    performed that Sunnah before its time. Hence it will not be counted as a 
    regular sunnah prayer; rather it is a naafil prayer between the adhaan and 
    iqaamah, for which one earns the reward of a naafil prayer, not a regular 
    Sunnah prayer. 

    An-Nawawi (may Allah have mercy on him) said: It is mustahabb 
    to pray two rak‘ahs or more before ‘Isha’, because of the hadeeth of 
    ‘Abdullah ibn Maghfal, according to which the Prophet (blessings and peace 
    of Allah be upon him) said: “Between each two calls (the adhaan and iqaamah) 
    there should be a prayer, between each two calls there should be a prayer, 
    between each two calls there should be a prayer” – and the third time he 
    said, “for whoever wishes.” Narrated by al-Bukhaari and Muslim. What is 
    meant by the two calls is the adhaan and iqaamah, according to scholarly 
    consensus.

    End quote from al-Majmoo‘, 3/504 

    For more information please see the answer to question no.
    128164

    With regard to the one who used to do that and was unaware of 
    the ruling as mentioned above, then we hope that Allah, by His bounty and 
    grace, will grant him the reward of one who offered the regular Sunnah 
    prayer, because he was unaware of the ruling on that matter.

    And Allah knows best.