Paul McCartney has said that the origin of “Mother Mary” is not Mary the Mother of Jesus, but rather his own mother, Mary Mohin McCartney, who had died of cancer when he was 14.  McCartney had a dream about his mother during the tumultuous period when the double-LP The Beatles – a/k/a the White Album – was being recorded; he recalled (as quoted in Wikipedia):  “‘It was great to visit with her again.  I felt very blessed to have that dream.  So that got me writing “Let it Be”.’  He also said in a later interview about the dream that his mother had told him, ‘It will be all right, just let it be.’  When asked if the song referred to the Virgin Mary, however, McCartney has typically answered the question by assuring his fans that they can interpret the song however they would like.”  

(September 2014)