So what is the Nazarite vow? It is first found in the Old Testament (then known as the Torah), in Numbers 6:1-21. It is a special "vow of separation to the LORD" that the Israelites made (Numbers 6:2).
The commands that a Nazarite must follow when he takes the vow are as follows:
"he must abstain from wine and other fermented drink and must not drink vinegar made from wine or from other fermented drink. He must not drink grape juice or eat grapes or raisins. As long as he is a Nazarite, he must not eat anything that comes from the grapevine, not even the seeds or skins. During the entire period of his vow of separation no razor may be used on his head. He must be holy until the period of his separation to the LORD is over; he must let the hair of his head grow long. Throughout the period of his separation to the LORD he must not go near a dead body" (Numbers 6:3-6).
I speculate that the vows abstention from wine points to the renunciation of earthly Joys in order to separate oneself and find all joy in the Lord. The unusually long hair symbolized the dedication of personal strength and vitality to the Lord. It was most likely an identifying physical mark of the individual's vow to the world. Furthermore, it was a reminder to meditate on the Lord and not be focused on ones outward appearance in this image conscious world.
There are two different types of Nazaritism, the temporary and the perpetual. The temporary is the type of vow that Paul took and is far more common in the Bible. One that takes the perpetual vow is a Nazarite from birth. There are only three perpetual Nazarites mentioned in the Bible; Samson, Samuel and John the Baptist.
With all of this in mind, the question still stands; "Are dreadlocks in the Bible?" Regrettably, I cannot give you a definitive answer either way. Although, given the spirit of the Nazarite vow I cannot imagine someone like John the Baptist combing his hair regularly. He was a priests son that chose to roam the desert instead of serving in the temple. His "clothes were made of camel's hair/skin, and he had a leather belt around his waist. His food was locusts and wild honey"(Matt 3:4). This guy more than likely wore the camel's hair inside out with the skin showing. His simple food and lifestyle were in and of themselves a visual protest against self indulgence and society itself. Again, I cannot imagine someone that lived in such a way spending the effort and time that it takes to groom thirty years worth of hair growth daily to keep it from tangling and knotting up. But since the Bible does not say clearly "He had dreads," one can only hypothesize.
The closest that we can get to a definitive answer regarding the presence of dreads in the Bible is found in the story of Samson and Delilah (Judges 16:13,19). Two times in this chapter it states that Samson had "Seven Locks"(KJV, NAS, RSV and Modern Language Versions). However, the NIV translates them as "Seven Braids" What we do know is that Samson's Israelite heritage originated from an area that today is the dividing gap between Africa and the Middle East. Given his ancestry, chances are he had course or woolly hair. Considering his vow and lifestyle, I cannot imagine this guy regularly combing and untangling hair that fell to his knees. In my heart I believe that Samson had seven fat dread locks.