David Sandeman: "I am head-to-foot righteousness"

In yesterday's message we reflected on 2 Peter 3:13:  "Nevertheless we, according to His promise, look for new heavens and a new earth in which righteousness dwells."

What is meant here by "righteousness"?  It could refer (1) to God the Father; (2) to Christ; or (3) to the saints (those made righteous or justified by faith, Rom 5:1).  

David Sandeman (1826-1858) was a Scottish missionary to China who became sick with cholera and died at the age of 32 years.  As he lay dying, a friend asked how he was doing.  He answered, "I am head-to-foot righteousness" (as cited in Iain Murray, The Old Evangelicalism, p. 73).