if I were to take a human being as a khaliil, it would be Abu Bakr...

Narrated by Aisha (Radhiallaho anho):

Abu Bakr came riding his horse from his dwelling place in
As-Sunh. He got down from it, entered the Mosque and did not
speak with anybody till he came to me and went direct to the
Prophet (sallallaahu 'alaihi wasallam), who was covered with
a marked blanket. Abu Bakr uncovered his face. He knelt down
and kissed him and then started weeping and said, "My father
and my mother be sacrificed for you, O Allah's Prophet!
Allah will not combine two deaths on you. You have died the
death which was written for you."

Narrated Abu Salama from Ibn Abbas: Abu Bakr came out and
'Umar was addressing the people, and Abu Bakr told him to
sit down but 'Umar refused. Abu Bakr again told him to sit
down but 'Umar again refused. Then Abu Bakr recited the
Tashah-hud (i.e. none has the right to be worshipped but
Allah and Muhammad is Allah's Messenger) and the people
attended to Abu Bakr and left 'Umar. Abu Bakr said, "Amma
ba'du (to proceed), whoever amongst you worshipped
Muhammad, then Muhammad is dead, but whoever worshipped
Allah, Allah is alive and will never die. Allah said:
'Muhammad is no more than an Prophet and indeed (many)
Prophets have passed away before him ..(up to the)
grateful.' " (Sura Al-e-Imran : Ver. 144) (The narrator
added, "By Allah, it was as if the people never knew
that Allah had revealed this verse before till Abu Bakr
recited it and then whoever heard it, started reciting
it.")

Bukhari Vol. 2 : No. 333