Fiqh-us-Sunnah, Volume 2: Nonstressed Sunnah Prayers (As-Sunan Ghair Al-Mu'akkadah)
We have been discussing the sunnah prayers which were stressed by the Prophet and which he was careful not to miss. There are some other sunnah prayers (al-sunan ar-ratibah) which are commendable, but are not "stressed."Volume 2, Page 10b: Two or four rak'at before 'asr
Many ahadith have been related about this sunnah prayer and they all support each other.
Such hadith include the following:
Ibn 'Umar reports that the Prophet said: "May Allah have mercy on a person who prays four rak'at before 'asr prayer." This was related by Ahmad, Abu Dawud, at-Tirmizhi (who calls it hasan), Ibn Hibban, and Ibn Khuzaimah. The latter two hold it as sahih. 'Ali reports that the Prophet sallallahu alehi wasallam prayed four rak'at before 'asr while separating every two sets of rak'at with salutations to the angels close to Allah, to the prophets, and to those who followed them - the believers and Muslims. This is related by Ahmad, an-Nasa'i, Ibn Majah, and atTirmizhi who grades it hasan.
As for praying only two rak'af at this time, this would fall under the generality of the Prophet's statement: "Between every azhan and iqamah there is a prayer."Volume 2, Page 10c: Two rak'at before maghrib
Al-Bukhari records, from 'Abdullah ibn Mughaffal, that the Prophet said: "Pray before maghrib, pray before maghrib," and after saying it a third time, he said: "For whoever wishes to do so," not wanting the people to take it as a sunnah. Ibn Hibban records that the Prophet prayed two rak'at before maghrib prayer.
Muslim records that Ibn 'Abbas said: "We would pray two rak'at before maghrib, and the Prophet would see us but he would not order us to do so, nor would he prohibit us."
Ibn Hajar says in Fath al-Bari: "All of the evidence points to the fact that it is preferred to say these two rak'at quickly like the two rak'at before the salatul fajr."Volume 2, Page 11: Two rak'at before salatul 'isha
'Abdullah Ibn Mughaffal reports that the Prophet said: "Between every azhan and iqamah there is a prayer. Between every azhan and iqamah there is a prayer." And, after saying it a third time, he said: "For whoever wishes [to pray it]." This is related by the group. Ibn Hibban records from Ibn az-Zubair that the Prophet said: "There exists no obligatory prayer without there being, immediately preceding it, two rak'at."Volume 2, Page 11a: Separating The Obligatory Prayer From The Supererogatory
It is preferred to make a separation between the fard and nawafil prayers after one finishes the fard prayer.
One of the companions of the Prophet sallallahu alehi wasallam reports that the Prophet prayed the afternoon prayer and right afterward a man stood up to pray. 'Umar saw him and told him: "Sit, the People of the Book were destroyed because they did not differentiate between their prayers." The Prophet said: "Well said, Ibn al-Khattab [i.e., 'Umar]." This is related by Ahmad with a sahih chain.