The Key to Paradise (Ahadith 1028 - 1029)


Bismillah.

Kitaab-ul-Janaa'iz [Book of Funerals] starts today.

Volume 2, Book 23, Number 329:
Narrated Abu Dhar:
Allah's Apostle said, "Someone came to me from my Lord and gave me the news (or good tidings) that if any of my followers dies worshipping none (in any way) along with Allah, he will enter Paradise." I asked, "Even if he committed illegal sexual intercourse (adultery) and theft?" He replied, "Even if he committed illegal sexual intercourse (adultery) and theft."
Volume 2, Book 23, Number 330:
Narrated 'Abdullah:
Allah's Apostle said, "Anyone who dies worshipping others along with Allah will definitely enter the Fire." I said, "Anyone who dies worshipping none along with Allah will definitely enter Paradise."
Small yet profound statements. It is important to understand them fully.
Key to Paradise = la ilaha illa Allah. No doubt in that. But there's a condition: one must die on this kalimah (phrase/sentence), meaning he should believe in it till he dies.
Let's look at different scenarios.
Case I:
Dies a Muslim (insert proper definition of Muslim here, i.e. one who submits his will to Allah) with no major sins.
Destination: Paradise.

الَّذِينَ يَجْتَنِبُونَ كَبَائِرَ الْإِثْمِ وَالْفَوَاحِشَ إِلَّا اللَّمَمَ ۚ إِنَّ رَبَّكَ وَاسِعُ الْمَغْفِرَةِ

"Those who avoid great sins (See the Qur'an, Verses: 6:152,153) and Al-Fawahish (illegal sexual intercourse) except the small faults, - verily, your Lord is of Vast Forgiveness." [An-Najm: 32]
BUT, must go through this for explanation.
Case II:
Dies a disbeliever/mushrik (polytheist).
Destination: Hell-fire.

إن الله لا يغفر أن يشرك به ويغفر ما دون ذلك لمن يشاء 

"Verily, Allah forgives not that partners should be set up with Him (in worship), but He forgives except that (anything else) to whom He wills.." [An-Nisaa': 48]
Case III:
Dies a Muslim with major sins (after repentance).
Destination: Paradise.
Shaykh al-Islam Ibn Taymiyah (may Allah have mercy on him) said:
If a person repents from sin, Allah will forgive him, whether it was shirk or otherwise, as He says (interpretation of the meaning):
“Say: O ‘Ibaadi (My slaves) who have transgressed against themselves (by committing evil deeds and sins)! Despair not of the Mercy of Allaah, verily, Allaah forgives all sins. Truly, He is Oft‑Forgiving, Most Merciful”
[al-Zumar 39:53]. 
Ibn al-Qayyim (may Allah have mercy on him) said:
If a person repents sincerely, his previous bad deeds will be erased and the reward for his good deeds will be restored for him.
End quote from al-Waabil as-Sayyib, p. 12 
Case IV:
Dies a Muslim with major sins (without repentance).
Destination: Unknown.
As for Case IV, scholars have given different opinions. You can go through detailed discussions here and here. But here's the gist: Allah knows best. He'll judge. Let's leave it on Him. :)
Wassalam.