Is it permissible to offer the prayer [for example, Asr] early?

It is not permissible to offer the prayer before its appointed time, because the Lawgiver has specified a beginning and an end for each prayer. However, the Lawgiver has granted a concession to Muslims to offer the Asr and Isha prayers earlier than their appointed times in two situations: travel and rain. Thus, it is permissible for a traveler to offer Asr early and combine it with Dhuhr, and likewise Isha with Maghrib. As for rain, it permits offering Isha early, combined with Maghrib, only for those who pray in congregation in the mosque, and it is not permitted for those who pray in their homes.