After the Prophet’s death, Bilal was reluctant to deliver the call to prayer, as he may have felt dissatisfied with succession arrangements. Reportedly, he declined to pledge allegiance (bay‘a) to Abu Bakr (r. 11–13/632–634) as caliph, and he eventually emigrated and settled in Sham. [1]
On at least one moving occasion, Bilal is known to have delivered the adhan after the Prophet, and that was upon the request of Muhammad’s beloved daughter Fatima (d. 11/632) and her two sons, al-Hasan (d. 50/669) and al-Husayn (d. 61/680). [1]
Reference
[1] Meri, Josef
W. “Medieval Islamic Civilization: An Encyclopedia”. Routledge,
NY. 2005, p. 109 ISBN 978-0-41-596690-0