Yesodei HaTorah 2:11
The concepts that we have discussed in these first two chapters are like a drop of water from an ocean of what is really required to explain things. The explanation of the principles discussed in these chapters is known as Maaseh Merkava, “the work of the Divine chariot.”
Yesodei HaTorah 2:12
The Sages ruled that these profound matters should not only be taught to just one student at a time, but that this student must be a wise person who can achieve understanding. If that is the case, he is given the basic points and an outline of the general concepts. He is then to contemplate the matter until he achieves his fullest possible understanding of these esoteric ideas. These ideas are so profound, however, that not everyone possesses the necessary knowledge to appreciate them. King Solomon described them as “Lambs for your clothing” (Proverbs 27:26). The Sages interpreted this metaphor to mean that the secrets of the universe should be like one’s clothes – for the individual alone, not for public consumption.
Along these lines, Proverbs 5:17 teaches, “They will be for you alone and not for outsiders along with you,” and Shir HaShirim 4:11 says, “Honey and milk are under your tongue.” The Sages understood this metaphor to mean that topics that are like honey and milk should be kept under one’s tongue.