Galatians 4:10

Ye observe (parathreisqe). Present middle indicative of old verb to stand beside and watch carefully, sometimes with evil intent as in Luke 6:7, but often with scrupulous care as here (so in Dio Cassius and Josephus). The meticulous observance of the Pharisees Paul knew to a nicety. It hurt him to the quick after his own merciful deliverance to see these Gentile Christians drawn into this spider-web of Judaizing Christians, once set free, now enslaved again. Paul does not itemize the "days" (Sabbaths, fast-days, feast-days, new moons) nor the "months" (Isaiah 66:23) which were particularly observed in the exile nor the "seasons" (passover, pentecost, tabernacles, etc.) nor the "years" (sabbatical years every seventh year and the Year of Jubilee). Paul does not object to these observances for he kept them himself as a Jew. He objected to Gentiles taking to them as a means of salvation.