Hadith taken from Sahih Bukhari:

Volume 8, Book 75, Number 350:
Narrated Anas:
Allah's Apostle said, "When anyone of you appeal to Allah for something, he
should ask with determination and should not say, 'O Allah, if You wish,
give me.', for nobody can force Allah to do something against His Will.

Reference: Sahih Bukhari
Invocations , Translation of Sahih Bukhari
Translator: M. Muhsin Khan


Volume 8, Book 75, Number 351:
Narrated Abu Huraira:
Allah's Apostle said, "None of you should say: 'O Allah, forgive me if You
wish; O Allah, be merciful to me if You wish,' but he should always appeal
to Allah with determination, for nobody can force Allah to do something
against His Will."

Reference: Sahih Bukhari
Invocations , Translation of Sahih Bukhari
Translator: M. Muhsin Khan


Hadith taken from Sahih Muslim:

Book 35. KITAB AL-DHIKR
(BOOK PERTAINING TO THE REMEMBRANCE OF ALLAH, SUPPLICATION, REPENTANCE AND
SEEKING OF FORGIVENESS
Chapter3 : SUPPLICATION SHOULD BE MADE WITH CONVICTION AND WILL

Book 035, Number 6479:
Abu Huraira reported Allah's Messenger (may peace be upon him) as saying:
None of you should say to Allah (like this): O Allah, grant me mercy, if
thou so likest. The supplication (of his) should (be permeated with)
conviction (that it would be accepted by the Lord), for Allah is the Doer of
(everything) He likes to do, and there is none to force Him (to do or not to
do this or that).

Book 35, Number 6477:
Anas reported Allah's Messenger (may peace be upon him) as saying: When one
of you makes supplication, he should supplicate with a will and should not
say: O Allah, confer upon me if Thou likest, for there is none to coerce
Allah.

Book 35, Number 6478:
Abu Huraira reported Allah's Messenger (may peace be upon him) as saying:
When one of you makes a supplication (to his Lord) one should not say: O
Allah, grant me pardon, if Thou so likest, but one should beg one's (Lord)
with a will and full devotion, for there is nothing so great in the eye of
Allah which He cannot grant.

Book 35, Number 6479:
Abu Huraira reported Allah's Messenger (may peace be upon him) as saying:
None of you should say to Allah (like this): O Allah, grant me mercy, if
thou so likest. The supplication (of his) should (be permeated with)
conviction (that it would be accepted by the Lord), for Allah is the Doer of
(everything) He likes to do, and there is none to force Him (to do or not to
do this or that).

Translation of Sahih Muslim
Translator: Abdul Hamid Siddiqui