Source : Webster's Revised Unabridged Dictionary (1913)

Diligently \Dil"i*gent*ly\, adv.
   In a diligent manner; not carelessly; not negligently; with
   industry or assiduity.

         Ye diligently keep commandments of the Lord your God.
                                                  --Deut. vi.
                                                  17.

Source : WordNet®

diligently
     adv : with diligence; in a diligent manner; "we may diligently
           observe the Lord's supper on the first day of the week,
           diligently preach the gospel, or minister to the saint"