{That} (hina). Probably ellipse (gen(8874)ai to be supplied)
as is common in Paul's Epistles ( 2Th 2:3  2Co 8:13  Ga 1:20  2:9  Ro 4:16  13:1  15:3 ). Some explain the imperative
kauchasth(935c) as an anacoluthon. The shortened quotation is from
 Jer 9:24 . Deissmann notes the importance of these closing
verses concerning the origin of Paul's congregations from the
lower classes in the large towns as "one of the most important
historical witnesses to Primitive Christianity" (_New Light on
the N.T._, p. 7; _Light from the Ancient East_, pp. 7, 14, 60,
142).