urah Yunus, Ayat 94-95

Ayat 94. So if you are in doubt concerning that which We have revealed (the Quran) unto you, [i.e. that your name is written in the Taurat (Torah) and the Injeel (Gospel)] then ask those who are reading the Book [the Taurat (Torah) and the Injeel (Gospel)] before you. Verily, the truth has come to you from your Lord. So be not of those who doubt (it).

Ayat 95. And be not one of those who belie the Ayat (proofs, evidences, verses, lessons, signs, revelations, etc.) of Allah, for then you shall be one of the losers. 

Hazrat Abu Hurairah (May Allah be pleased with him) reported: Messenger of Allah  [SAWW](PBUH) said, "Follow the Right Path of Faith strictly, and be steadfast; and keep in mind that none of you can achieve salvation through his (good) actions.'' Someone asked, "Not even you, O Messenger of Allah?'' He  [SAWW](PBUH) said, "Not even me, unless Allah grants me His Mercy and Grace". [Muslim Book 39, Hadith Number 6762].

Lesson : as mentioned above in Surah Yunus Ayat 95. "And be not one of those who belie the Ayat of Allah, for then you shall be one of the losers." This Hadith tells us that although the importance of Faith and its practice is beyond any shadow of doubt, because this is the only way to attain His Favours and Blessings, but one should not entirely depend upon practice only because any shortcoming (which one does not even know) can ruin a good deed. It is, therefore, essential that we also pray that our good deeds are accepted by Allah and that He grants us His Infinite Mercy and sincerity because even the greatest noble deed is invalid without it.