who . . . least = to the less than the least. Greek. elachistoteros. Only here. That is what Paul was. What he became, see 1Co_15:10 (laboured more abundantly, &c).
saints. In Eph_3:5, "holy". See Act_9:13.
is = was.
preach. App-121.
among = to.
unsearchable = untraceable. Only here and Rom_11:33, which see.