It is almost impossible to fulfill this obligation

Parshas Hashavua/ Daf Hashavua (Pesachim 13a)

והייתם נקיים מה' ומישראל

The Chasam Sofer (Shut 6 : 59) writes. "There are two obligations 

1) To come clean from Hashem

2) from Bnei Yisroel. 

It is much easier to fulfill the first obligation than the second one. The punishment for the second

obligation is also much greater. (Chillul Hashem).

You can have a person doing something which is Halachicly  correct, but isn't careful  and some

"שותי שכר" (beer drinkers) mistakenly accuse him of wrongdoing, such a person has not  fulfilled his

obligation of והייתם נקיים .

It is almost impossible to fulfill this obligation. It is likely Shlomo Hamelech had this in mind when he

wrote this אין צדיק בארץ

We find in this weeks Parsha the Bnei Gad etc. followed Moishe Rabbeinu's advice and fought along

with the other Shevatim for 14 years. They were punished  to be sent to Galus before the rest of Klall

Yisroel, because* they haven't fulfilled 100% the obligation of והייתם נקיים ."

*see Midrash Rabbah (Matos) other reasons