What is the ruling on someone who forgot to wash under their armpits or behind their ears during ghusl? And what is meant by renewing the intention?

Among the conditions for the validity of ghusl (ritual bath) is the complete coverage of the entire body with water. So, whoever neglects washing a part of his body, such as his armpits or a part of his head, his ghusl is considered incomplete, and his prayers are invalid.

If a Muslim forgets to wash a limb and a long time passes, he should wash that limb with a new intention to remove the ritual impurity, and his ghusl will be valid. However, he must repeat the prayers he performed before washing the forgotten limb.