(15) See then that ye walk circumspectly, not as fools, but as wise,
(16) Redeeming the time, because the days are evil.
(17) Wherefore be ye not unwise, but understanding what the will of the Lord is.
We already understand that we must walk wisely and redeem the time. Beyond that, though, we are to understand the will of the Lord - what it is. How do we know God's will? We must redeem the time and instead of seeking after this world's ideas, seek first God and His kingdom.
1 Thessalonians 4:3-6 - For this is the will of God, even your sanctification, that ye should abstain from fornication: That every one of you should know how to possess his vessel in sanctification and honour; Not in the lust of concupiscence, even as the Gentiles which know not God: That no man go beyond and defraud his brother in any matter: because that the Lord is the avenger of all such, as we also have forewarned you and testified.
Sanctification (38) hagiasmos (hag-ee-as-mos'); from NT:37; properly, purification, i.e. (the state) purity; concretely (by Hebraism) a purifier:
Should abstain (567) apechomai (ap-ekh'-om-ahee); middle voice (reflexively) of NT:568; to hold oneself off, i.e. refrain:
Fornication (4202) porneia (por-ni'-ah); from NT:4203; harlotry (including adultery and incest); figuratively, idolatry:
Honor (5092) time (tee-may'); from NT:5099; a value, i.e. money paid, or (concretely and collectively) valuables; by analogy, esteem (especially of the highest degree), or the dignity itself:
Lust (3806) pathos (path'-os); from the alternate of NT:3958; properly, suffering ("pathos"), i.e. (subjectively) a passion (especially concupiscence):
Concupiscence (1939) epithumia (ep-ee-thoo-mee'-ah); from NT:1937; a longing (especially for what is forbidden):
Defraud (4122) pleonekteo (pleh-on-cek-teh'-o); from NT:4123; to be covetous, i.e. (by implication) to over-reach:
If, after reading this passage and looking up definitions, one comes away with the mindset that "God doesn't care about purity," they must be blind!!!! This verse seems to clear that it is God's will that all of His children should live in purity - though applicable spiritually, this passage is specifically talking about physically.
1 Thessalonians 5:18 - In every thing give thanks: for this is the will of God in Christ Jesus concerning you.
God's will is that we give thanks in every thing (good and bad).
Hebrews 10:36 - For ye have need of patience, that, after ye have done the will of God, ye might receive the promise.
Again, there is the will of God for our individual lives. However, this verse encourages us to be patient, because if we have done God's will, we will also receive His promise. Ultimately, this is talking about Christ's promised return (Heb 10:37), but given the verses previous, applies to many aspects of life.