Once your mind is moved by great compassion, you will definitely make the commitment to free all living beings from cyclic existence. If your compassion is weak, you will not.
Therefore, compassion is important in the begining because feeling responsible to free all beings requires great compassion and because, if you do not take on this responsibility, you are not ranked as a Mahayana practitioner.
Also the Foremost of Gaya states:
“Manjusri, what is it that motivates the bodhisattva deeds?
What is its object?”
Manjusri said,
“Devaputra, great compassion motivates the bodhisattva deeds; its object is living beings.”
Thus compassion is the basis of engaging in the deeds because when you see that you will not live up to your commitment without training in the two vast collections, you set about the difficult work of amassing these vast collections.
You may develop the spirit of enlightenment at one time and then engage in the bodhisattva deeds.
But when you see that living beings are innumerable and act improperly, that the training is very difficult and limitless, and that you need an immeasurable length of time, you may lose heart and fall into the Hinayana.
And how do we avoid that? We will discuss these special concepts in our classes. As you see, there are indeed so much we need to learn!