Explanation:

- Option 1: Savigny – He was a historical jurist who focused on law as a manifestation of the "spirit of the people" (Volksgeist). He did not explicitly make the statement that statutes are sources of law, not part of law itself.

- Option 2: Austin – As a positivist, he viewed law as the command of the sovereign, seeing statutes as actual law, not just sources.

- Option 3: Gray – Correct Answer. John Chipman Gray argued that statutes are sources of law but not laws themselves until interpreted by courts. The law is what the courts say it is.

- Option 4: Pound – He was a sociological jurist and distinguished between law as rules laid down and as actually practiced, but the famous statement is not attributed to him.