Charles H. Spurgeon on Psalms 139:2

My thought. The er, rea, which we have rendered "thought", signifies also a friend or companion, on which account some read —thou knowest what is nearest me afar off, a meaning more to the point than any other, if it could be supported by example. The reference would then be very appropriately to the fact that the most distant objects are contemplated as near by God. Some for "afar off" read beforehand, in which signification the Hebrew word is elsewhere taken; as if he had said, O Lord, every thought which I conceive in my heart is already known to thee beforehand. —John Calvin.