Before he became a Buddha, there is no Buddhist teaching. Hindu teaching is definitely there. It is too naïve to think that Buddha and his followers only know 1 language.
In Hindu, Sanskrit is also the language of Hinduism. During that time, we cannot say I only know Pali, I don’t know Sanskrit, or vice versa. Someone can know several languages. Since Buddha has been exposed to Hindu culture, we cannot say he only know Pali or Magadhi. Siddhartha Gautama crossed many regions in India. He doesn’t just stay in 1 region. He himself is also exposed to Hindu culture, where Sanskrit is already quite common during that period.
His followers are not only from 1 region, but from several regions speaking different languages. We cannot say none of his followers only knows Pali, or only Sanskrit. His followers may know few other languages.
According to the best guess of historians, Buddha spoke Magadhi. However, can the historian guess Siddhartha only know Magadhi? He doesn’t know Pali, Sanskrit, or other dialects?
In fact, if we think Buddha spoke Magadhi, all scriptures in Pali should be rejected.
Although some claims Magadhi is similar with Pali, no matter how you think, they are different. Just because some words may be similar, it doesn’t mean if I say Magadhi, you who speak Pali can fully understand what I say.
If the language alone is the criteria to check the validity of dharma, only dharma text in Magadhi should be accepted as authentic.
Besides that, none of them are authentic, not Pali, nor Sanskrit.
The writing of Dharma heavily depends on his students. Do you think his students are only exposed to 1 language? If previously his student is Brahmin and Hindu background, where he is more familiar to Sanskrit, why he has to write down what he has learnt only in Magadhi, only in Pali, or only in Sanskrit ?
Chinese, African, and Western go to Thailand to study under 1 teacher who speaks Thai. The students know Thai. However, when they come back to their own country, there is no reason why the students cannot record the teaching in their own languages.
Do you think during Buddha’s time, his students cannot write down or make a note what they has learned? Do you think all of his students have exceptional memory, where they can remember exactly what the Buddha has spoken? Do you think Buddha dharma in writing is only available after Buddha’s death? Do you think there are no missing personal notes? Do you think the students cannot make small note depending on their mother tongue, whether it is Magadhi, Pali, or Sanskrit?
Thinking the authenticity of Buddhist teaching can only appear in 1 language is actually already weird. India is a multicultural country and multi languages. Buddha himself across so many regions and having so many students with different backgrounds and different mother tongues.
Based on what reasons the authenticity of Buddha dharma has to simply appear in just 1 language?
I am not here nor there.
I am not right nor wrong.
I do not exist neither non-exist.
I am not I nor non-I.
I am not in samsara nor nirvana.
To All Buddhas, I bow down for the teaching of emptiness. Thank You!