What is the ruling on someone who missed the Isha prayer and remembered it at the time of the Fajr Adhan? Is it valid for him to complete it? And what must a person do when making up missed prayers, whether consecutive or separate? Is it necessary to say, "I intend to pray the obligatory prayer of... such-and-such... as a missed prayer incumbent upon me for the sake of Allah, Lord of the worlds," when making them up?

It is not permissible to delay prayer beyond its prescribed time due to work engagements; rather, it must be performed on time, in congregation if possible. If a worshipper begins the 'Isha prayer and hears the Fajr Adhan (definition), they should not interrupt their prayer; for it is either being performed on time (if the Adhan is before the true dawn) or being made up (if it is after). Whoever misses obligatory prayers must make them up. Sequencing them is obligatory according to the Hanbalis without exception, and according to the Hanafis and Malikis if the prayers are few (four or five). Sequencing is recommended according to the Shafi'is. For the validity of the prayer, it is not a condition to intend whether it is performed on time or being made up, and it is not legislated to vocalize the intention for prayer.