Fiqh-us-Sunnah Volume 1, Purification and Prayer, Fiqh 1.056.

Scholars also encourage Muslims to perform ghusl for the ‘id prayers, even though there is no authentic hadith to support this opinion. It says in al-Badr alMuneer, “The hadith concerning performing ghusl for the ‘ids are weak. But there do exist good reports from the companions (on this point).”