The Pulpit Commentary on Acts 24:16

Herein … also for and hereby, A.V. and T.R.; to have a conscience … always for to hare always, etc., A.V.; and men for and toward men, A.V. (For the sentiment, comp. Acts 23:1.) Herein ( ἐν τόυτῳ); i.

e. on this account, under these circumstances supplying the ground and cause of my action (comp. John 16:30). So, too, Matthew 6:7, ἐν τῇ πολυλογίᾳ αὐτῶν means "On account of their much speaking."

I exercise myself; ἀσκῶ, here only in the New Testament, but frequent in medical writers for "to practice" the medical art.