A.T. Robertson Commentary Acts 20:26

"Wherefore I testify unto you this day, that I am pure from the blood of all men." — Acts 20:26 (ASV)

I testify (μαρτυρομα). Elsewhere in the N.T. only in Paul's Epistles (Galatians 5:3; Ephesians 4:17; 1 Thessalonians 2:12). It means "I call to witness" while μαρτυρεω means "I bear witness."

This day (εν τη σημερον ημερα). The today day, the last day with you, our parting day.

I am pure from the blood of all men (καθαρος ειμ απο του αιματος παντων). Paul was sensitive on this point as in Corinth (Acts 18:6). It is much for any preacher to claim and it ought to be true of all. The papyri also give this use of απο with the ablative rather than the mere ablative after καθαρος.