A.T. Robertson Commentary 1 Thessalonians 3:10

"night and day praying exceedingly that we may see your face, and may perfect that which is lacking in your faith?" — 1 Thessalonians 3:10 (ASV)

Exceedingly (υπερεκπερισσου). Double compound adverb, only in 1 Thessalonians 3:10; 5:13 (some MSS. -ως). Like piling Ossa on Pelion, περισσως, abundantly, εκ περισσου, out of bounds, υπερεκπερισσου, more than out of bounds (overflowing all bounds).

And perfect (κα καταρτισα). First aorist active articular infinitive of purpose (εις το ιδειν--κα) of καταρτιζω, to mend nets (Matthew 4:21) or men (Galatians 6:1) repair. Chiefly late.

That which is lacking in (τα υστερηματα). The shortcomings, the lacks or left-overs (Colossians 1:24). From υστερεω (υστερον), to be late.