6)  All beings have Buddha nature.
Just as milk is pervaded by butter
When the two accumulations1 are ‘churned’ with effort
At some point Buddha nature will manifest! That is my heart advice. 

This verse teaches that all sentient beings have the essence of Buddhahood. All sentient beings are primordially Buddhas but, not realizing it, bedazzled by fleeting deception, sentient beings wander in samsara. As said in Sutra,

Sentient beings are nothing but Buddhas
But they are obscured by fleeting defilements.
Dispelling the defilements, they are actually Buddhas.

As said, all sentient beings intrinsically have Buddha nature, the cause that we may become a Buddha. Described by many examples, like butter pervading milk, like oil pervading sesame seeds, like gold pervading ore, no matter how bad sentient beings have been, they are all pervaded by Buddha nature.

Excerpt of text written by Khenpo Karten Rinpoche, from the book Precious Teachings, chapter entitled “A Door of Entrance to the Heart Advice Called A Ship Sailing to Liberation:  A Commentary on the Heartfelt Advice of Dharma Nectar,” page 125 in the paper book, and page 133 in the PDF version.