9. known God or rather are known of God--They did not first know and love God, but God first, in His electing love, knew and loved them as His, and therefore attracted them to the saving knowledge of Him (Mt 7:23; 1Co 8:3; 2Ti 2:19; compare Ex 33:12, 17; Joh 15:16; Php 3:12). God's great grace in this made their fall from it the more heinous.
      how--expressing indignant wonder at such a thing being possible, and even actually occurring (Ga 1:6). "How is it that ye turn back again?"
      weak--powerless to justify: in contrast to the justifying power of faith (Ga 3:24; compare Heb 7:18).
      beggarly--contrasted with the riches of the inheritance of believers in Christ (Eph 1:18). The state of the "child" (Ga 4:1) is weak, as not having attained manhood; "beggarly," as not having attained the inheritance.
      elements--"rudiments." It is as if a schoolmaster should go back to learning the A, B, C'S [BENGEL].
      again--There are two Greek words in the original. "Ye desire again, beginning afresh, to be in bondage." Though the Galatians, as Gentiles, had never been under the Mosaic yoke, yet they had been under "the elements of the world" (Ga 4:3): the common designation for the Jewish and Gentile systems alike, in contrast to the Gospel (however superior the Jewish was to the Gentile). Both systems consisted in outward worship and cleaved to sensible forms. Both were in bondage to the elements of sense, as though these could give the justification and sanctification which the inner and spiritual power of God alone could bestow.
      ye desire--or "will." Will-worship is not acceptable to God (Col 2:18, 23).

JFB.