Answer:
of his use of the expression "is-salamu alaykum"
Step-by-step explanation:
The Egyptian authorities gave an expression of displeasure and were disappointed at Hakim because the Hakim used in his expression and said "is-salamu alaykum".
It is in Arabic. It is most common form of greetings among the Muslim people to say that 'peace be upon you'. This greeting is generally deployed when people of Muslim faith meet each other or interact with each other.
Thus the Egyptian authorities were disappointed when Hakim used the phrase "is-salamu alaykum".
Hence the answer is --
of his use of the expression "is-salamu alaykum"