Is one sinful if one delays the Dhuhr prayer beyond its time in order to attend a lecture?

A Muslim must perform congregational prayer on time unless there is an excuse, for the Prophet, peace and blessings be upon him, said: "Whoever hears the call to prayer and does not come, there is no prayer for him except for one with an excuse," and for Allah Almighty's saying: {Indeed, prayer has been decreed upon the believers at specified times.}

If an excuse arises that permits abandoning the congregation or combining two prayers, then it is permissible without sin. If the combination is by delaying, then one should intend, at the time of the first prayer, to delay it.

Among the excuses that permit combining prayers, according to some scholars, is if one fears harm to their livelihood were they to not combine them.

Therefore, if a Muslim is unable to leave a lecture or delay it beyond the prayer time, and cannot do without it due to harm that would affect their livelihood, then this is an excuse that permits abandoning congregational prayer and praying individually. If they are unable to do so, then it is permissible for them to combine the two prayers until the excuse is removed.