The report of Rigdon preaching from John Chapter 16 is from Richard S. Van Wagoner. 1994. Sidney Rigdon: A Portrait of Religious Excess. Signature Books, p. 640.
Rigdon also reportedly also preached from John Chapter 15 while a Reformed Baptist:
“At length Bishop R. arose — read John xv. ch. and prayed. Another hymn was sang — Bishop R. then, after making some introductory remarks, named for his subject, obedience. He exhibited Jesus as the Lord of Lords and King of Kings — considered the gospel as addressed to all without exception, who hear it; and enforced its exhortations with the promise of life and salvation.”