My Word is My Honour

Hurmuzan, the leader of the Persians, was brought to Umar Radhi Allahu Anhu as a prisoner.
Umar Radhi Allahu Anhu addressed him, “I present Islam to you in good counsel for your immediate and future endeavours.”
Hurmuzan replied, “I believe firmly in the religion I currently follow. I have no inclination towards Islam.”
Umar Radhi Allahu Anhu was about to behead him, but he requested, “Can I have a sip of water, instead of dying of thirst?”
Umar Radhi Allahu Anhu instructed that he be given some water to drink.
With the water in his hand, he asked, “Am I safe until I drink it?”
“Yes,” replied Umar Radhi Allahu Anhu.
He then threw the water onto the ground and said, “Honour your word!”
Umar Radhi Allahu Anhu replied, “You have my word. You shall be left alone until we think the matter over.”
At this, Hurmuzan said, “Now I proclaim that there is no deity worthy of worship besides Allah and that Muḥammad is His servant and messenger. Whatever he proclaimed was the truth.”
Umar Radhi Allahu Anhu said, “You are now a Muslim, but what delayed you in accepting Islam?”
Hurmuzan answered, “I did not want people to think that I had accepted Islam out of fear.”
Upon this, Umar Radhi Allahu Anhu remarked, “The Persians have such intelligence which has entitled them to rule over vast dominions.” Umar Radhi Allahu Anhu then ordered that Hurmuzan be treated kindly.
Umar Radhi Allahu Anhu would then consult him regarding military matters dealing with the Persians.

Reference : Pearls from the Path, Volume 2;  p171