Delaying Prayer Beyond its Time
Q: Can I delay Asr pray beyond its chosen time / waqt al-mukhtar for the sake of praying in a congregation?
A: It is not permissible for anyone who is obliged, mindful, and capable of praying to delay prayer, or a part thereof, beyond its permitted time / waqt al-jawaz (for prayers with one time) or its chosen time / waqt al-mukhtar (for prayers that have two times). Doing so is in direct violation of the command to pray on time. It is permitted to delay the prayer beyond the above-mentioned times due to a legitimate legal excuse such as combing prayers when permitted and is required when trying to meet a condition of prayer which can be completed relatively quickly, even if the time expires, such as purification or mending a ripped garment which exposes the ‘awrah. If fulfilling that condition will take a significant time, like someone having to go purchase new clothes far away or having no way to determine the direction of the qiblah, the prayer must be made on time as is.
Delaying the prayer in this manner to pray in a congregation is not a valid excuse.
It should be noted that delaying the prayer without excuse is sinful but still valid and must be made. Missing the prayer does not remove the obligation to make it. For prayer with two times, if it is delayed beyond its chosen time / waqt al-mukhtar without excuse it is still considered a prayer offered and not one made up.
Source: Kashshaf al-Qina, Sharh al-Muntaha, al-Insaf