DOCSP-21990 BACKPORT (#959)

Author: Dave

source/tutorial/install-mongodb-on-os-x.txt

@@ -106,6 +106,12 @@ Follow these steps to install MongoDB |edition| Edition using Homebrew's
    If you have already done this for a previous installation of MongoDB,
    you can skip this step.
 
+#. To update Homebrew and all existing formulae:
+
+   .. code-block:: bash
+
+      brew update
+
 #. To install MongoDB, run the following command in your macOS Terminal
    application: