question #3 Sahih Muslim 685a, Book 6, Hadith 1 : Why was an addition made to the number of rak’ahs for prayers at the place of residence?

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.