A sincere witness from the Children of Israel put aside racial pride and recognizes, and testifies that the Koran is from Allah 46:10-14
46:10 Say, 'Consider, if this (Koran) is from Allah and you disbelieve in it, and a witness from the Children of Israel testifies to its like and believes, while you are proud! Indeed, Allah does not guide the harm doers.'
46:11 The unbelievers say of the believers, 'Had it been any good they would not have believed in it before us.' And because they are not guided by it they say, 'This is an ancient falsehood.'
46:12 Yet before it there was the Book of Moses which was an authority, and a mercy. This (Koran) is the Book confirming it (the other untampered Books) in the Arabic tongue, to warn the harm doers and to give glad tidings to those who do good.