Should we return to the custom of not trimming our beards, as Leviticus 19:27 says? Leviticus 19 v 27 says “Do not cut the hair at the sides of your head or clip off the edges of your beard.”
A law given by God
This was a law given by God to the people of Israel when they were in Sinai. A beard, in their culture and in some cultures today, was and is a badge of manly dignity. When God made this rule, the Israelites had recently left Egypt where men usually shaved their heads and face. Shaving the beard in Israel was for the ceremony of cleansing (Lev. 14:9), a sign of humiliation (2 Sam. 10:4, 5), or a sign of mourning (Jer. 41:5). Plucking out the beard (Ezra 9:3) was a sign of frustration, anger, or mourning.
Heathen religions of the time shaved their beards, and heads in specific ways for divination or to honour spirits and gods. The people of Israel were forbidden from following the customs of the people around them, see Leviticus 21:5 and Deuteronomy 14:1. This did not mean however that they were just to leave their beards to grow long and unkempt (2 Samuel 19:24). Mephibosheth had not looked after himself, or trimmed his hair and beard as a sign of mourning, until David returned safely. The Bible actually does not make any specific reference to how one should care for his facial hair, but it is obvious that they were to care for themselves and not allow themselves to be unkempt.
Guidance for today
This is the only guidance we have for today. Whether people have beards today is not the issue: our cultures are completely different, but we should look after our bodies, (as temples of the living God, 1 Corinthians 3:16,17) and glorify God in how we live.