[MNDude]

Numbers 6:1-21 details the Nazirite vow, a special vow of dedication to God in ancient Israel.

Throughout the period of the vow, a Nazirite was not to cut their hair. This resulted in long hair being a visible sign of their dedication.

There is ample evidence many Jews in the first century followed this.

In Acts 21:23-26, the Apostle Paul takes part in a purification ritual related to the Nazirite vow. Paul sponsors several men who are under a vow and pays for their temple sacrifices, demonstrating that the practice was alive and well among early Christians and Jews in the first century.

[Olog-hai]

Jesus was a Nazarene, not ever described as a Nazirite. And he would have been in serious breach of such a vow during His ministry had He taken such a vow, given His eating and drinking habits.

[Ruy Dias de Bivar]

Jewish Christians but not Gentile Christians.
Acts 21
20 When they heard this, they praised God. Then they said to Paul: “You see, brother, how many thousands of Jews have believed, and all of them are zealous for the law. 21 They have been informed that you teach all the Jews who live among the Gentiles to turn away from Moses, telling them not to circumcise their children or live according to our customs. 22 What shall we do? They will certainly hear that you have come, 23 so do what we tell you. There are four men with us who have made a vow.

24 Take these men, join in their purification rites and pay their expenses, so that they can have their heads shaved. Then everyone will know there is no truth in these reports about you, but that you yourself are living in obedience to the law.

25 As for the Gentile believers, we have written to them our decision that they should abstain from food sacrificed to idols, from blood, from the meat of strangled animals and from sexual immorality.”