My relative from USA was also challenged that Gurbani mentions no afterlife. The faithless person believed in "ਇਹ ਜਗ ਮਿੱਠਾ ਅਗਲਾ ਕਿੰਨ ਡਿੱਠਾ'' ("This life is for enjoyment, who has seen the next life!"). He stated that Gurbani doesn't believe in Dharam-Raaj (the righteous judge who judges us when we die), heaven(s), hell(s), reincarnation, or Sach Khand. He went further to argue that we can do whatever we like and should "enjoy" life (his reference to drink alcohol, eat meat, and enjoy the desires of the mind). Whether someone believes or doesn't believe does not bother me - however it is bothering when someone tries to justify their own views incorrectly with Gurbani (despite no quotations to back up what they are saying!).
First of all, a Sikh believes that Gurbani is the Word of God and therefore for a Sikh Gurbani is a 'fact', the absolute truth and direct from God. Gurbani is a mirror showing us reality!
ਸਤਿਗੁਰ ਕੀ ਬਾਣੀ ਸਤਿ ਸਤਿ ਕਰਿ ਜਾਣਹੁ ਗੁਰਸਿਖਹੁ ਹਰਿ ਕਰਤਾ ਆਪਿ ਮੁਹਹੁ ਕਢਾਏ ॥"O GurSikhs! Know that the Bani, the Word of the True Guru, is true, absolutely true. The Creator Lord Himself causes the Guru to chant it."(Ang 308)
In Japji Sahib we read:
ਕਚ ਪਕਾਈ ਓਥੈ ਪਾਇ || ਨਾਨਕ ਗਇਆ ਜਾਪੈ ਜਾਇ ||੩੪||"The ripe and the unripe, the good and the bad, shall there be judged. O Nanak! Going there, this is made known. ||34||"(Ang 7)
ਚੰਗਿਆਈਆ ਬੁਰਿਆਈਆ ਵਾਚੈ ਧਰਮੁ ਹਦੂਰਿ ॥"Good deeds and bad deeds-the record is read out in the Presence of the Lord of Dharma."(Ang 8)
When I started off on the journey of Sikhi as a young teenager I met various people who shared their views about Sikhi. One view which I was exposed to was that Dharam-Raaj (the Righteous Judge), Chitar-Gupt (divine scribes who note down every action and thought we take), Jamdoots (the messengers of death) etc do not exist in reality. Gurbani mentions all these concepts, but I was told that these things have been mentioned as mere references to help explain the message to the people. I was told that Dharam-Raaj is my conscience (because my conscience judges what I do) and Chitar-Gupt are my subconsciousness (because that records all my thoughts and deeds). When I started meeting Gursikhs and they mentioned Dharam-Raaj or Chitar-Gupt, I would get confused - do they really exist or is it metaphorical?
Once, I sat down to do Keertan at home. Just before opening the Amrit-Keertan Pothi to find a Shabad, a thought came in my "Guru jee - Is Dharam-Raaj real or is it just a metaphorical concept?" I just opened the Amrit-Keertan Pothi and Guru jee answered my question with the Shabad appearing on the page...
ਧਰਮ ਰਾਇ ਹੈ, ਹਰਿ ਕਾ ਕੀਆ, ਹਰਿ ਜਨ ਸੇਵਕ ਨੇੜਿ ਨ ਆਵੈ ॥
"Dharam-Rai, the Righteous Judge of Dharma exists; he is a creation of the Lord; he does not approach the humble servant of the Lord."
Guru jee is amazing! Why question what Gurbani says! If Gurbani says something then it means it!
As for explaining the afterlife, Guru jee says:
ਨਾਨਕ ਜੀਅ ਉਪਾਇ ਕੈ ਲਿਖਿ ਨਾਵੈ ਧਰਮੁ ਬਹਾਲਿਆ ॥
ਓਥੈ ਸਚੇ ਹੀ ਸਚਿ ਨਿਬੜੈ ਚੁਣਿ ਵਖਿ ਕਢੇ ਜਜਮਾਲਿਆ ॥
ਥਾਉ ਨ ਪਾਇਨਿ ਕੂੜਿਆਰ ਮੁਹ ਕਾਲ੍ਹ੍ਹੈ ਦੋਜਕਿ ਚਾਲਿਆ ॥
ਤੇਰੈ ਨਾਇ ਰਤੇ ਸੇ ਜਿਣਿ ਗਏ ਹਾਰਿ ਗਏ ਸਿ ਠਗਣ ਵਾਲਿਆ ॥
ਲਿਖਿ ਨਾਵੈ ਧਰਮੁ ਬਹਾਲਿਆ ॥੨॥
"Pauree: O Nanak! Having created the souls, the Lord installed the Righteous Judge of Dharma to read and record their accounts. There, only the Truth is judged true; the sinners are picked out and separated. The false find no place there, and they go to hell with their faces blackened. Those who are imbued with Your Name win, while the cheaters lose. The Lord installed the Righteous Judge of Dharma to read and record the accounts. ||2||"
(Ang 463 - taken from Aasa Ki Vaar)
ਨਾਮੁ ਵਿਸਾਰਿ ਦੋਖ ਦੁਖ ਸਹੀਐ ॥ ਹੁਕਮੁ ਭਇਆ ਚਲਣਾ ਕਿਉ ਰਹੀਐ ॥
ਨਰਕ ਕੂਪ ਮਹਿ ਗੋਤੇ ਖਾਵੈ ਜਿਉ ਜਲ ਤੇ ਬਾਹਰਿ ਮੀਨਾ ਹੇ ॥੮॥
ਚਉਰਾਸੀਹ ਨਰਕ ਸਾਕਤੁ ਭੋਗਾਈਐ ॥ ਜੈਸਾ ਕੀਚੈ ਤੈਸੋ ਪਾਈਐ ॥
ਸਤਿਗੁਰ ਬਾਝਹੁ ਮੁਕਤਿ ਨ ਹੋਈ ਕਿਰਤਿ ਬਾਧਾ ਗ੍ਰਸਿ ਦੀਨਾ ਹੇ ॥੯॥
ਖੰਡੇ ਧਾਰ ਗਲੀ ਅਤਿ ਭੀੜੀ ॥ ਲੇਖਾ ਲੀਜੈ ਤਿਲ ਜਿਉ ਪੀੜੀ ॥
ਮਾਤ ਪਿਤਾ ਕਲਤ੍ਰ ਸੁਤ ਬੇਲੀ ਨਾਹੀ ਬਿਨੁ ਹਰਿ ਰਸ ਮੁਕਤਿ ਨ ਕੀਨਾ ਹੇ ॥੧੦॥
"Forgetting the Naam, one suffers the misery of his evil ways. When the order to depart is issued, how can they remain here? They fall into the pit of hell, and suffers like a fish out of water. ||8|| The faithless cynic has to endure 8.4 million hellish incarnations. As they act, so do they suffer. Without the True Guru, there is no liberation. Bound and gagged by their own actions, they are helpless. ||9|| This path is very narrow, like the sharp edge of a sword. When their account is read, they shall be crushed like the sesame seed in the mill. Mother, father, spouse and child - none is anyone's friend in the end. Without the Lord's Love, no one is liberated. ||10||" (Ang 1028)