Cannot Be Taught
Mahamudra cannot be taught, but
You, who practiced austerities for the teacher from devotion
And patiently bore sufferings, intelligent Naropa
Fortunate one, listen to this and take it to your heart
Tilopa was a yogi who gathered together the tantric teachings as well as teachings on mahmudra and passed them onto Naropa. Naropa was originally a monk and a scholar, one of the four principal teachers at the Buddhist monastic school, Nalanda. At that time it was not possible to be a monk and a tantric practitioner. But Naropa's zeal for finding the truth was so great that he left the monastery, went searching for Tilopa as a teacher, and underwent hardship as his student.
Finding the truth is not hard, but it does require one hundred percent of your effort. The German theosophist Rudolf Steiner once explained the difference between chemistry and alchemy, saying that in chemistry you are holding a test tube over a flame, but in alchemy you are in the test tube getting cooked. Meditation is exactly like that. You cannit do it casually or at arm's length of you want to see the truth. It has to be a complete commitment. And that is how Naropa practiced.
The first line says that mahamudra cannot be taught. This is for two reasons. First, mahamudra is something that needs to pacticed and not learned. You cannot learn to meditate from someone else, you need to practice it yourself and learn from that.
The second reason mahamudra cannot be taught requires explaining some Buddhist philosophy. According to this philosophy, the first moment of perception is free of thoughts. In subsequent moments, the perception of the object is replaced with a generalized concept about the object. For example, in the first moment you see the car as it actually is, but after that the perception becomes one instance of the more generalized idea of a car. You classify it, categorize it, and judge it. The practice of mahamudra is to remain in that original moment of thought as much as possible. Because this moment precedes thoughts and concepts, it cannot be taught.