Is it permissible to fast three days of every month without specifying particular days, knowing that the White Days exist?

It is recommended to fast three days every month, and there is no harm in them being at the beginning, middle, or end of the month. These days differ from the 'white days' (Ayyam al-Bid), which are also recommended to fast. It has been authentically reported that the Prophet (peace be upon him) advised fasting three days every month, and that fasting the 'white days' is like fasting for an entire year.

It was narrated from Aisha (may Allah be pleased with her) that the Prophet (peace be upon him) used to fast three days every month, and he did not care from which part of the month he fasted them.

So, fasting the 'white days' is recommended, and likewise, fasting three days every month is recommended, whether they are consecutive or separate.