Extracts from William Clayton's Private Book
A Key by Joseph Smith Dec
1840—W[illiam]. C[layton]. 
If an Angel or spirit appears offer him your hand; if he is a spirit from God he will stand still and not offer you his hand. If from the Devil he will either shrink back from you or offer his hand,  which if he does you will feel nothing, but be deceived.
A good Spirit will not decieve.
Angels are beings who have bodies and appear to men in the form of man.
 The following report is here published for the first time. William Clayton, an English convert, arrived in Nauvoo 24 November 1840.
 William Clayton (1814-79). A convert from England, Clayton was given numerous clerical assignments in Nauvoo, including recording the Prophet's sermons and assisting with his correspondence.
 Unlike other versions of these instructions given by Joseph Smith from 1839 to 1843, this account indicates that the Devil is not compelled to "offer his hand." Apparently Joseph Smith believed that the Devil had sense enough to avoid obvious detection but that unlike "a spirit from God," he would not remain motionless (Moses 1:11-23; 4:6; see also 27 June 1839, note 21.