And - omitted in the oldest manuscripts (compare Eph 6:7, Eph 6:8). Compare the same principle in the case of all men, Hezekiah (2Ch 31:21; Rom 12:11).
do, do it - two distinct Greek verbs, “Whatsoever ye do, work at it” (or “labor at” it).
heartily - not from servile constraint, but with hearty good will.