Charles Ellicott Commentary Acts 26:5

"having knowledge of me from the first, if they be willing to testify, that after the straitest sect of our religion I lived a Pharisee." — Acts 26:5 (ASV)

After the most straitest sect.—Better, most rigid, or most precise. The Greek does not contain anything answering to the double superlative of the English. The word for “sect” is the same as that used in Acts 24:5, and translated “heresy” in Acts 24:14.