«كُنَّا فِي الْبَيْطَرَهْ صِرْنَا فِي الْحِكْمَهْ»

The saying describes a conversation that set out on one subject, the treatment of animals, and has arrived somewhere else entirely, at the practice of medicine. Here الحكمة means medicine, set against البيطرة, not its more familiar sense of 'wisdom'.

It is applied whenever discussion strays from the matter at hand. By naming both the starting subject and the one reached, the speaker draws attention to the digression itself and to the fact that the original topic has been left behind.

Say it when a conversation has moved off its intended subject and onto another, to point out that the discussion has wandered from what was originally being talked about.