Is it permissible to combine several Sunnah prayers, or to combine them with the obligatory (Fard) prayer?

It is permissible to combine two acts of worship with a single intention if they are intertwined, such as the ghusl for Jumu'ah and janabah, or if one of them is not intended for its own sake, like the greeting of the mosque along with another prayer. However, combining two acts of worship that are each intended for their own sake is not valid, such as the Dhuhr prayer and its regular Sunnah prayer. Thus, it is permissible to combine more than one Sunnah prayer in a single prayer, such as Salat al-Istikhara and the two rak'ahs of Shaf' (even-numbered), or Salat al-Hajah and the two rak'ahs of Fajr. Similarly, a fard (obligatory) prayer or a regular Sunnah prayer suffices for the Sunnah of Wudu' and the greeting of the mosque because they are not intended for their own sake.