"Night of the three Caliphs": <a href="https://en.wikipedia.org/wiki/Harun_al-Rashid" id="mwHQ" rel="mw:WikiLink" title="Harun al-Rashid">Harun al-Rashid</a> becomes the Abbasid caliph upon the death of his brother <a href="https://en.wikipedia.org/wiki/Al-Hadi" id="mwHg" rel="mw:WikiLink" title="Al-Hadi">al-Hadi</a>. Birth of Harun's son <a href="https://en.wikipedia.org/wiki/Al-Ma'mun" id="mwHw" rel="mw:WikiLink" title="Al-Ma'mun">al-Ma'mun</a>.<sup about="#mwt15" class="mw-ref reference" data-mw='{"name":"ref","attrs":{},"body":{"id":"mw-reference-text-cite_note-1"}}' id="cite_ref-1" rel="dc:references" typeof="mw:Extension/ref"><a href="./September_14#cite_note-1" id="mwIA" style="counter-reset: mw-Ref 1;"><span class="mw-reflink-text" id="mwIQ">[1]</span></a></sup>
<span class="mw-reference-text" id="mw-reference-text-cite_note-1"><cite about="#mwt12" class="citation web cs1" id="CITEREFRekaya2012">Rekaya, M. (24 April 2012). <a class="external text" href="https://referenceworks.brillonline.com/entries/encyclopaedia-of-islam-2/al-mamun-SIM_4889" id="mwCEU" rel="mw:ExtLink nofollow">"al-Maʾmūn"</a>. <i id="mwCEY">Encyclopaedia of Islam, Second Edition</i><span class="reference-accessdate" id="mwCEc">. Retrieved <span class="nowrap" id="mwCEg">March 11,</span> 2019</span>.</cite><span about="#mwt12" class="Z3988" id="mwCEk" title="ctx_ver=Z39.88-2004&amp;rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&amp;rft.genre=unknown&amp;rft.jtitle=Encyclopaedia+of+Islam%2C+Second+Edition&amp;rft.atitle=al-Ma%CA%BEm%C5%ABn&amp;rft.date=2012-04-24&amp;rft.aulast=Rekaya&amp;rft.aufirst=M.&amp;rft_id=https%3A%2F%2Freferenceworks.brillonline.com%2Fentries%2Fencyclopaedia-of-islam-2%2Fal-mamun-SIM_4889&amp;rfr_id=info%3Asid%2Fen.wikipedia.org%3ASeptember+14"></span></span>