(19) باب إِقْبَالِ الْمَحِيضِ وَإِدْبَارِهِ
Narrated `Aisha:
Fatima bint Abi Hubaish used to have bleeding in between the periods, so she asked the Prophet (ﷺ) about it. He replied, "The bleeding is from a blood vessel and not the menses. So give up the prayers when the (real) menses begins and when it has finished, take a bath and start praying."
Reference: Sahih al-Bukhari 320
In-book reference: Book 6, Hadith 25
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 1, Book 6, Hadith 317