The following is excerpted from The Sutra of Hui Neng (also known as the Platform Sutra), Chapter 5 entitled ‘On Dhyana’. My comments are interspersed in italicised red:

Learned Audience, what are Dhyana and Samadhi? Dhyana means to be free from attachment to all outer objects, and Samadhi means to attain inner peace. If we are attached to outer objects, our inner mind will be perturbed.

Tom: we can see Hui Neng has succinctly defined both Dhyana and Samadhi. In the next line he is essentially saying that these two are one and the same, in that when there is no attachment (ie. Dhyana), there will also be peace (ie. Samadhi):

When we are free from attachment to all outer objects, the mind will be in peace.

Tom: See if you can see the parallel with Sri Ramana Maharshi stating in ‘Who Am I?’:

‘Not to desire anything extraneous to oneself constitutes vairagya (dispassion) or nirasa (desirelessness). Not to give up one’s hold on the Self constitutes jnana (knowledge). But really vairagya and jnana are one and the same.’

Our Essence of Mind is intrinsically pure, and the reason why we are perturbed is because we allow ourselves to be carried away by the circumstances we are in.

He who is able to keep his mind unperturbed, irrespective of circumstances, has attained Samadhi.

Tom: Sri Ramana Maharshi states in ‘Who Am I?’: ‘If only the mind is kept under control, what matters it where one may happen to be?’

In the above two lines Hui Neng hints that your True Nature, or what Hui Neng refers to as Essence of Mind, is already ‘unperturbed’, and essentially is always undisturbed and ‘pure’. Realisation of this naturally leads to Freedom:

To be free from attachment to all outer objects is Dhyana, and to attain inner peace is Samadhi. When we are in a position to deal with Dhyana and to keep our inner mind in Samadhi, then we are said to have attained Dhyana and Samadhi. The Bodhisattva Sila Sutra says, “Our Essence of Mind is intrinsically pure.” Learned Audience, let us realize this for ourselves at all times. Let us train ourselves, practice it by ourselves, and attain Buddhahood by our own effort.