Should he fast on the fifteenth of Sha’baan even if the hadeeth is da’eef? : An answer to the question: “Is it permissible, even after finding out that a hadeeth is da’eef (weak), to follow it, by way of doing righteous deeds? The hadeeth says: “When it is halfway through Sha’baan, spend that night in prayer and fast on that day.” The fast is observed as a voluntary act of devotion to Allaah, as is spending that night in prayer (qiyaam al-layl).

A Brief Illustrated Guide To Understanding Islam