The Ruling on Combining the Prayers. without an Excuse
Question :
Is it permissible to combine the Zuhr and 'Asr prayers every day?
Answer:
It is not permissible to combine the afternoon or the evening prayers without a valid excuse, such as continuous travel or rain which soaks the clothes and causes mud to adhere to the feet, or such as illness which makes Wudhu' a burden etc.
Source:
Ibn Jibreen
Fatawa Islamiyah, Vol. 2 Page 222