All thoughts arise either on the basis of body or speech. Thoughts such as “my body”, “my head”, “my legs”, “my hands”, and so on arise from the basis of the body. Thoughts such as “this is good”, “this is bad”, “this is pure”, “this is dirty”, “this is a friend”, “this is an enemy”, and so on arise on the basis of terms, the expressions of speech. All thoughts that arise on the basis of the body and the ones that arise on the basis of speech equally occur in connection with names. Thus all thoughts arise on the basis of terms and are therefore just nominal. Freedom from conceptual elaboration is the state of peace in which all thoughts have subsided.
Buddha Nature: The Mahayana Uttaratantra Shastra with Commentary
explanation by Khenpo Tsultrim Gyamtso Rinpoche
This is an excellent book and one of the few available in English on the subject. Great supplementary reading for Gyumed Khensur Rinpoche Losang Jampa’s on-going teachings at the Gyuto Vajrayana Center. I’ve just excerpted part of a longer passage from Khenpo la’s commentary, I encourage you to read it in its entirety (see page 349).