Wilford Woodruff records Joseph Smith's teachings on detecting Angels.
"Discourse, 27 June 1839, as Reported by Wilford Woodruff," The Joseph Smith Papers, accessed July 26, 2023
[Drawing of a key.]
As there are many keys to the kingdom of God the following one will detect Satan when he transforms himself nigh unto an angel of light When Satan appears in the form of a personage unto man & reaches out his hand unto him & the man takes hold of his hand & feels no substan[c]e he may know it is Satan for an angel of God (which is an angel of light) is a Saint with his resurrected body & when he appears unto man & offers him his hand & the man feels a substance when he takes hold of it as he would in shaking hands with his neighbour he may know it is a Angel of God. & should a Saint appear unto man whose body is not resurrectd he will never offer him his hand for it would be against the law by which they are governd & by observing this key we may detect Satan that he decieve us not