Gurfateh
As per Sanatan Sikhs(Sikhs following the idealogy that Gurmat(Sikhism) was here since the world came into being) Holy Vedas,Holy Bible and Holy Kuran are books from God.
For them you can visit
www.sarbloh.info
Coming for the views of Das or any other Sikh likie him even in Guru Granth Sahib ji there are verses from holy men who were not Sikh and were before First Master Shri Guru Nanakdev Sahib Ji. And those verse are considered as delvered by God.
Guru Granth Sahib ji state that God since ages have created devotees and have proteected there respect.
in the nutshell Sikhism is not anti to faith before it but it is complemewntory to them. Like thoery of say Phythogoras was made in remote past.
While demovier and present day mathmaticians have made very advances theroies which are not anti to pythagour but complemtory.
Had there been no misinterpetations being done by eveil in acceint scritpure and was well then What was the reason of Guru to be sent on earth by Akal(God of Sikhs).
As per Gurmat regarding revalations.
Sabhe Ghat Ram Bole ie in all atoms does God(Absorbed in there) Speaks(ie acts).
So in the faith where God is omni observed it is unlikly to see for go after revalations only by supernatural ways.