"Praise Nietzsche," the 'Rebel Heart' singer wrote alongside the mysterious quote.
The message comes amid reports that Madonna and ex-husband Guy Ritchie are fighting for custody over their eldest son, Rocco.
Miley Cyrus and Madonna are big fans of one another.
The 'Joy' actress admitted to Graham Norton that she's 'never had a good one.
Despite fighting over Rocco with her ex-husband in court, the Material Girl still took the time to express her love on Instagram.
The 57-year-old singer posted the sweet message amid reports that her son was court ordered to return to her New York home.
Madonna's son, Rocco, reportedly wants to stay with his dad, Guy Ritchie, in London, but the pop singer is not having it.
The singer filed new legal documents on Thursday spelling out that -- contrary to persistent tabloid rumors -- she was never physically assaulted by Penn during their marriage.
Madonna is refuting the prevalent tabloid rumors that Sean Penn abused her.
The singer calls rumors of domestic abuse 'completely outrageous.'
The pop icon paid tribute to those slain in the recent terrorist attacks.
The 57-year-old singer couldn't hold back her tears while giving a moving speech to her fans following the terror attacks in France.
'I gave Madonna a spanking,' 'The Martian' star wrote on Facebook.
Mila Kunis, Ashton Kutcher and Fergie also attended the concert.
