question #3 Sahih Muslim 685a, Book 6, Hadith 1 : How does the modification of prayer rak’ahs reflect the adaptability of Islamic practices to different circumstances?

The prayer was prescribed as two rak’ahs, two rak’ahs both in journey and at the place of residence. The prayer while travelling remained as it was (originally prescribed), but an addition was made in the prayer (observed) at the place of residence.