Salam alaikum warahmatullah brothers and sisters fasting on the 15 of Sha baan is an innovation (Bid ah ) in Islam and the Hadith that says we should fast on the 15 of Sha baan is a week Hadith is not authentic The Prophet PBUH says The most truthful word is the word of Allah, and the best way is the way of Muhammad PBUH, and the worst thing in that way is invention ,and each invention leads to innovation , and each innovation leads to misguidance and misguidance leads to Jahannam (hell fire ) So please whatever of form of worship you want do in Islam make sure you do a research about it and base it on the Quran and sunnah with authentic Hadith ✍️ Wallahu alaam .