{Ye observe} (parat(8872)eisthe). Present middle indicative of
old verb to stand beside and watch carefully, sometimes with evil
intent as in  Lu 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"
( Isa 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.