J. B. Lightfoot on Colossians 4:15-16

ἀναγνωσθῇ παρ’ ὑμῖν ἡ ἐπιστολή, ποιήσατε ἵνα καὶ 16. ἡ ἐπιστολή] ‘_the letter_’, which has just been concluded, for these salutations have the character of a postscript; comp. Rom. xvi. 22 Τέρτιος ὁ γράψας τὴν ἐπιστολήν, 2 Thess. iii. 14 διὰ τῆς ἐπιστολῆς, _Mart. Polyc._ 20 τὴν ἐπιστολὴν διαπέμψασθε. Such examples however do not countenance the explanation which refers ἔγραψα ὑμῖν ἐν τῇ ἐπιστολῇ in 1 Cor. v. 9 to the First Epistle itself, occurring (as it does) in the middle of the letter (comp. 2 Cor. vii. 8). ποιήσατε ἵνα] ‘_cause that_’; so John xi. 37, Apoc. xiii. 15. In such cases the ἵνα is passing away from its earlier sense of _design_ to its later sense of _result_. A corresponding classical expression is ποιεῖν ὡς or ὅπως, e.g. Xen. _Cyr._ vi. 3. 18. A similar charge is given in 1 Thess. v. 27. The precaution here is probably suggested by the distastefulness of the Apostle’s warnings, which might lead to the suppression of the letter.