Christians translate metanoia (Greek) as "to repent." It is often said that the word literally means to "change the mind." But, this is not the literal translation of the word metanoia. In fact, literally, it means "afterthought," and it can be translated as "reconsideration." In the context of rhetoric, metanoia is a rhetorical device used to retract or correct a statement just made, by stating it in a better way. It is in this context that the Hebrews intended it. The Hebrew version of this word is found at Job 21:34 "So how can you console me with your futile words? Nothing is left of your answers ( uT'$uVoTaykeM- "responses of yours") but deception!"
The boundaries of Jewish law are determined through the halakhic process, a religious-ethical system of legal reasoning. Rabbis generally base their opinions on the primary sources of Halakha as well as on precedent set by previous rabbinic opinions. The major sources and genre of Halakha consulted include one called she'eloth w-teshuvoth (שאלות ותשובות) (literally "petitions and responses"), or "responsa" (Latin) or teshuvot (Hebrew). Teshuvot (or singular teshuvah) play a particularly important role in the Jewish system of equity. Petitions forwarded are usually concerned with new contingencies for which no provision has been obviously made in the codes of law and the teshuvot thus supplement the codes, and represent the so-called "equity law." Because of this, the teshuvot deal mostly with issues of social or restorative justice (issues of equity). Thus, teshuvot represents the processes which seek to ensure the maintenance of a fair, equitable, egalitarian and generally harmonious society.
Yeshua utilized a method of she'eloth w-teshuvoth in the form of oral petitions/responses. Some of his responsa are clearly set out in the New Testament (see Mat 5:22; 5:28; 5:32; 5:34; 5:39; 5:44; 6:29; 8:11; 11:22; 11:24; 12:6; 12:36 Luke 6:27; 12:4; 12:8 and others).
Now, it was customary, among Jews of the first century, to be immersed in the mikveh before Yom Kippur as a sign of purity and repentance and before the Sabbath in order to sensitize oneself to the holiness of the day. Also, among Pharisees, it was customary to ritually immerse oneself (and hands, and foods, and eating utinsils, etc) many times daily. Ritual immersion (Greek Baptizo) served as a purity ritual separating (making holy) the initiates from those outside of the ritual.
The Gospel of Luke sets out a story of Yeshua and his opinion regarding such ritual cleansing:
Luke 11:37 And as He was speaking, a certain Pharisee asked Him that He would dine with him. And going in, He reclined. 38 But watching, the Pharisee marveled that He did not first wash before the dinner. Luke 39 But the Lord said to him, Now you Pharisees cleanse the outside of the cup and of the dish, but your inside is full of robbery and evil. Luke 40 Fools! Did not He who made the outside also make the inside? Luke 41 So, as it is possible, give compassion and behold, all things will be clean to you.
Mark 7:4 And coming from the market, if they do not immerse (baptize) themselves, they do not eat. And there are many other things which they received to hold: dippings (baptizm) of cups, and of utensils, and of copper vessels, and couches. Mark 7:5 Then the Pharisees and scribes questioned Him, Why do your disciples not walk according to the tradition of the elders, but eat bread with unwashed (anipto - without clean) hands? Mark 7:6 And answering, He said to them, Well did Isaiah prophesy concerning you, hypocrites; as it has been written: "This people honors Me with the lips, but their heart is far away from Me; Mark 7:7 and in vain they worship Me, teaching as doctrines the commandments of men." Isa. 29:13 Mark 7:8 For forsaking the commandment of God, you hold the tradition of men: baptism of utensils and cups, and many other such like things you do.
Yeshua further set out the needlessness of "washing" as a purity ritual, saying: (Mark 7:18) ...Are you also so undiscerning? Do you not perceive that all that enters from the outside into the man is not able to defile him.
The prophet Isaiah said:
Isa 58:1 Shout out loud! Don't hold back! Raise your voice like a shofar! Proclaim to my people what rebels they are, to the house of Ya'akov their sins. 2 "Oh yes, they seek me day after day and desire in knowing my ways. As if they were an upright nation that had not abandoned the rulings of their God, they ask me for just rulings (tzedekah mishpat) and [claim] to take pleasure in closeness to God, 3 [asking,] 'Why should we fast, if you don't see? Why mortify ourselves, if you don't notice?' "Here is my answer: when you fast, you go about doing whatever you like, while keeping your laborers hard at work. 4 Your fasts lead to quarreling and fighting, to lashing out with violent blows. On a day like today, fasting like yours will not make your voice heard on high. 5 "Is this the sort of fast I want, a day when a person mortifies himself? Is the object to hang your head like a reed and spread sackcloth and ashes under yourself? Is this what you call a fast, a day that pleases YAHWEH? 6 "Here is the sort of fast I want - releasing those unjustly bound, untying the thongs of the yoke, letting the oppressed go free, breaking every yoke, 7 sharing your food with the hungry, taking the homeless poor into your house, clothing the naked when you see them, fulfilling your duty to your kinsmen!" 8 Then your light will burst forth like the morning, your new skin will quickly grow over your wound; your righteousness will precede you, and YAHWEH's glory will follow you. 9 Then you will call, and YAHWEH will answer; you will cry, and he will say, "Here I am..."
Thus, Yeshua (as John before him) taught baptism, not of water, but of teshuva (english "Baptism of repentence" see Mark 1:4; Luke 3:3). That is to say, he taught that the way to purity (freedom from sin) lay in teshuva (doing equity) rather than in the rites and rituals of man.