Is he who prays a prayer that is not to be combined with the one following it, during the Adhan of the next prayer or its calendar time, considered to have delayed the prayer, bearing in mind the different scholarly opinions, especially the opinion of those who permitted eating and drinking during the Adhan?

It is not permissible to deliberately delay prayer beyond its prescribed time, and this is considered one of the major sins. So, whoever delays a prayer until the time for the next prayer has begun, has taken it out of its [prescribed] time. Delaying a prayer beyond the time specified in the approved calendar is considered delaying it.