Islamic scholars agree that:
"None of the noble individuals of the chain coming from Prophet Ibrahim (Abraham) to Prophet Muhammad (peace be upon them) was indifferent to the true religion and none of them blemished their heart with shirk (idol-worship, to associate anyone or anything with Allah) and kufr (disbelief, blasphemy)" (1)
Many Islamic scholars put forward with clear evidence that Prophet Muhammads (pbuh) parents will be among the people of salvation in the afterlife, through similar explanations.
We can list those explanations as follows:
1) His parents, Hazrat Abdullah and Hazrat Amina, passed away long before their son undertook the task of the prophethood. So, they lived in the period of (fatrat) interregnum and they are regarded as people of interregnum. There is no torment of Hell for those who died during the period of interregnum.
One day someone asked a well-known scholar Sharaf al-Din al-Munawi,
"Are our prophets parents in Hell?"
"They passed away during the interregnum. There is no torment before sending down a Prophet" (2)
It is well defined in the Quran and hadith (saying or tradition of the Prophet Muhammad) that no one who did not hear an invitation of a Prophet will have torment in the afterlife. (3) It is also known that no previous Prophets invitation reached Prophet Muhammads (pbuh) parents. So, we can say that they will have no torment in the afterlife and they are among the people of salvation.
2) There is no information that the Prophets parents were in shirk and kufr. On the contrary, they were among the Hanif people who were practicing the beliefs and traditions coming from their grandfather Prophet Ibrahim (pbuh), like Zayd Ibn Amr Ibn Nufayl, Waraqa Ibn Nawfal and others.
3) Another piece of evidence that they were not in shirk is a hadith of Prophet Muhammad (pbuh), "I come from a continuous line of clean fathers and always mothers" (4)
In the Quran, people of shirk is defined as unclean people. (5) Since cleanness and uncleanness, faith and shirk, believers and unbelievers are opposites, and when we consider the above hadith, we must accept that no one from the ancestors of Prophet Muhammad (pbuh) was in shirk. (6)
In short, While Prophet Muhammad (pbuh) is said to be a mercy to the universe by Allah, it would not be logical and harmonious with good manners to think that his parents, who carried him in their bodies before the sun of prophethood was born would be deprived of the prosperity and light of their sun. The parents of the Messenger of Allah lived in the Period of Ignorance (Jahiliyyah). They did not live during the time of the prophethood of Hazrat Muhammad (pbuh)
Then, a believer should know and accept the following:
The parents of Allahs Messenger are surely from the people of salvation, people of Paradise and people of belief. Surely Allah Almighty will not hurt His dear messengers tender and compassionate heart. (7)
The following stanza expresses that truth in a nice way:
While the sun of the two worlds were in the sign of bliss
How would Allah not give his parents honor?
Oh my heart! Look at the diver with equitable eyes
Would he take the pearl and throw away the mother-of pearl?
1. Maktubat p.397; Tajrid Translation, 4/537
2. Tajrid Translation, 4/539
3. Quran, Surah (chapter) of Isra (The Israelites), 15
4. Qadi Iyaz, 1/183
5. Quran, Surah of Tauba (Repentance), 28
6. Tajrid Translation, 4/546
7. Badiuzzaman Said Nursi, Mektubat, p.398