Ezekiel, chapter 37
10: So I prophesied as he commanded me, and the breath came into them, and they lived, and stood up upon their feet, an exceeding great army.
11: Then he said unto me, Son of man, these bones are the whole house of Israel: behold, they say, Our bones are dried, and our hope is lost: we are cut off for our parts.
12: Therefore prophesy and say unto them, Thus saith the Lord GOD; Behold, O my people, I will open your graves, and cause you to come up out of your graves, and bring you into the land of Israel.
13: And ye shall know that I am the LORD, when I have opened your graves, O my people, and brought you up out of your graves,
14: And shall put my spirit in you, and ye shall live, and I shall place you in your own land:
THEN shall ye know that I the LORD have spoken it, and performed it, saith the LORD.
Eph 2:8For by grace are ye saved through Knowledge (oops, I mean faith

and that not of yourselves: [it is] the gift of God:
No, I think Paul was telling them to examine themselves and prove whether they were Christians or reprobates. He certainly was asking them "don't you know whether you have Christ or not"?
It certainly was a question to them.
2Cr 13:5Examine yourselves, whether ye be in the faith; prove your own selves.
Know ye not your own selves, how that Jesus Christ is in you, except ye be reprobates?
If you are testing yourself to see if you are in the faith, then you are testing yourselves to see if Jesus Christ is in you.
If they KNEW, then there would of been no reason for the test.