http://qa.sunnipath.com/issue_view.a...8735&CATE=1352 "The recommendation of performing either two or four rakats before Isha is established by the general Prophetic recommendation to pray before each obligatory prayer (with the exception of Maghrib, because of the specific command to hasten its performance without delay). [Kasani, Bada'i` al-Sana'i`; Zayla`i, Tabyin al-Haqa'iq; Ibn Abidin, Radd al-Muhtar; Shurunbulali, Maraqi al-Falah; Nawawi, al-Majmu`]] "The Prophet (peace and blessings be upon him) said, "Between each set of calls to prayer [i.e. between each adhan and iqama] is a prayer." He repeated this three times, and then said, "For whoever wishes to do so." [Bukhari and Muslim from Abd Allah ibn Mughaffal (Allah be pleased with him)]. This is also the position of the Shafi`i school. [Nawawi, al-Majmu`]