Is there a sin for delaying a colleague from the Dhuhr prayer due to unintentional work circumstances, and what should be done about it?

The interpretation of the Almighty's saying: (And eat and drink until the white thread of dawn becomes distinct to you from the black thread of night)

The interpretation of this noble verse clarifies the end time for a fasting Muslim to eat and drink, which is the appearance of the true dawn (Al-Fajr Al-Sadiq), known by the first appearance of the dawn's whiteness on the horizon, distinguishing it from the blackness of the night.

So, the white thread is the whiteness of the true dawn, and the black thread is the blackness of the night. This is what the Prophet, peace be upon him, clarified to his noble Companions, saying: "That is only the whiteness of the day from the blackness of the night." (Narrated by Muslim)

Some Companions, like Adi ibn Hatim, may Allah be pleased with him, initially thought that the two threads referred to actual threads, until the Prophet, peace be upon him, clarified the correct meaning to them. (Narrated by Al-Bukhari and Muslim)

Accordingly, eating, drinking, and performing all acts that break the fast are permissible until the true dawn appears. When the dawn's appearance becomes clear, the fasting person must abstain from everything that breaks the fast. If the dawn appears while a person is eating or drinking, they must immediately stop eating and drinking. There is no harm in what was swallowed unintentionally before knowing of the dawn's appearance.

And Allah knows best.