It is narrated marfu‘an from Hazrat Abu Hurairah (may Allah be pleased with him) that when any one of you makes supplication, he should not say: "O Allah! If You will, forgive me," but rather he should supplicate with determination and certainty, for there is no one who can compel Allah.
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 7314