This is very important for people who are striving in the deen to comprehend. We will not approach Allah by removing the Sunnahs from our life . It has been the habit of the pious predecessors before us and the pious that will come after us to seek out every Sunnah that they can find..
The command of Allah is "Ateeullah war rasool---Obey Allah and His Messenger". In this day and age, we have a classification of our legal system, so we say that "This act is fardh, this act is waajib, this act is sunnah muakkadah, this act is sunnah ghair muakkadah, this act is nafl, this act is mustahab.....etc etc.".
However, the Companions (radiyallahu anhum) didn't make any distinction between fardh and Sunnah. Whatever they saw the Prophet S.A.W do, they did and whatever he told them to do, they did. There was no distinction at that time that "Oh this is fardh and this is a Sunnah" If it came from Rasoolullah S.A.W it was to be done. Period. They made no distinctions.
So, we have to be very, very clear that the Sunnah doesn't have to be something that can be jettisoned. We've clearly been told "Ateeullah war Rasool "
The Prophet (peace and blessings be upon him) is reported to have said: Whoever prays twelve Rak`at during the day and night will have a house built for him in Paradise.” (Reported by At-Tirmidhi)
The Messenger of Allah (salallahu alayhi wa sallam) laid great emphasis on the sunnah prayer of Fajr, saying, "It is more superior than the world and everything within it." (Sahih Muslim 1:151)
A'isha (radiallahu anha) said, "The Messenger of Allah (salallahu alayhi wa sallam) was not as regular in any supererogatory (nafl) prayer as he was in the two rak'ats before Fajr." (Sahih Muslim 1:251)
Dhuhr / Zohar
Aishah (May Allah be pleased with her) reported: The Prophet (sallallaahu ’alayhi wa sallam) never omitted four Rak`ah supererogatory prayer before Zuhr prayers. [Al-Bukhari].
Aishah (May Allah be pleased with her) reported: Whenever the Prophet (sallallaahu ’alayhi wa sallam) stayed in my house, he would perform four Rak`ah (supererogatory prayer) before Zuhr prayer. Then he would go out and lead Salat. He (sallallaahu ’alayhi wa sallam) would then come back and perform two Rak`ah (supererogatory prayer). He would lead the Maghrib prayer and come back and perform two Rak`ah (supererogatory prayer). When he (sallallaahu ’alayhi wa sallam) had led the `Isha' prayer, he would enter the house and perform two Rak`ah (supererogatory prayer). [Muslim]
Rasulullaah S.A.W said, "May Allah have mercy on a man who prays four before 'Asr." [Abu Datum 'Ali RA narrates that Rasulullah SAW used to pray two Rak'at before 'Asr. [Abu Dawood]
After Maghrib it is sunnah to pray 2 Rak'ahs. It is narrated by Ibn Umar (radiallahu anhuma) that the Prophet (salallahu alayhi wa salam) would not miss them. It is preferable to recite after al-Fatihah Surah Kafiroon and Surah Ikhlas. Ibn Masood (radiallahu anh) said: "I cannot count how many times i heard the Messenger of Allah (salallahu alayhi wa salam) recite, in the two rak'ahs after Maghrib and in the two rak'ahs before Fajr: Surah Kafiroon and Surah Ikhlas."
Hammad ibn Abi Sulayman said: "I asked Ibrahim about the salah before Maghrib, he forbade me from this and said: "The Prophet (SAW), Umar (RA), and Abu Bakr (RA) did not pray it." Imam Muhammad (RA) said: "We adhere to this. When the sun sets there is no salah on janazah or any other salah before the salah of Maghrib. And it is the opinion of Abu Hanifa (RA)."
The sunnah after Isha is 2 rak'aat. Performing 4 Rak'aat Before Salaat al-Isha is considered mustahab. Hadrat Sa’eed Ibn Jubair (radiallaahu 'anh) narrates that the Sahaabah (radiallaahu 'anhum) used to regard the performing of four rak'aat before the fard of 'ishaa as mustahab. [Qiyaamul-Layl of Marwazi pg.58]