He that comes from above is above all: he that is of the earth is earthly, and speaks of the earth…
In courts of law, in olden times, a witness gave his statement of that which he professed was truth. Having done so, parties present who were cognisant of the veracity of the speaker, or who were in circumstances that they might be expected to be so, when called on to testify their knowledge, in confirmation of what had been asserted, by doing this set to their seal that what had been spoken was true, and that the witness who had spoken was faithful. But parties who, being thus appealed to, and being qualified to testify, declined to speak in corroboration of the testimony delivered, were held, by that declining, to make the witness a liar. To this practice allusion is made in the text. God hath spoken by His Son to the world; He has spoken that which all men may know, that which all men are bound to know to be true, that they may be able to confirm it as His word of truth. Being commanded to become acquainted with the things which are spoken, they are then, as a great duty, commanded to bear testimony to the truth, to the veracity of Him by whom it has been uttered. When they refuse to know what God speaks, they offend against His authority. When they refuse to testify to the truth — to set to their seal that He is true in the Word which has been given to them — they offend against His veracity; they make Him a liar.
(A. Beith, D. D.)
Parallel VersesKJV: He that cometh from above is above all: he that is of the earth is earthly, and speaketh of the earth: he that cometh from heaven is above all.