How As-Salat (the Prayer) was prescribed on the night of Al-Isra (miraculous night journey) of the Prophet (pbuh) to Jerusalem (and then to the heavens)

Narrated `Aisha: the mother of believers: Allah enjoined the prayer when He enjoined it, it was two rak`at only (in every prayer) both when in residence or on journey. Then the prayers offered on journey remained the same, but (the rak`at of) the prayers for non-travelers were increased.