en_tn/2th/03/13.md

But

But - "but" contrasts between the lazy believers to the hard working believers.

you

this refers to the Thessalonians believers. (See: rc://en/ta/man/translate/figs-you)

do not lose heart

This is an idiom for "do not be discouraged". (See: rc://en/ta/man/translate/figs-idiom)

take note of him

"publicly identify that person" (UDB).