Bava Batra

And according to your reasoning,  [if] he sold [something] worth five for six  would his sale indeed be [legally] valid?  But [this is the reason]: The Rabbis were well aware that a child is susceptible to the temptations of money; and if it would have been laid down  [that] a sale of his is legally valid, [people] might sometimes rattle money before him [and] he would be tempted  to sell all the possessions of his [dead father]. In the case of a gift, however, [it is known that] had he not had [some] benefit from him  he would not have presented him with a gift; the Rabbis, [therefore.] said [that] his gift shall be a [legal] gift in order that people might render him service. R. Nahman said in the name of Samuel: [A youth] must be examined [to ascertain whether he has the signs of maturity]  in respect of betrothal,  divorce, halizah,  [declarations of] refusal.  But in regard to the sale of the estate of his father, he cannot do so until he becomes twenty years of age.  But since [the youth]  was examined in respect of his betrothal what need is there  [for an examination] in respect of [his] divorce?  — This [law] is required only [in the case] of a youth who married his dead brother's widow.  For we learnt: [If] a boy of the age of nine years and a day had connexion with his sister-in-law,  he has acquired her [as wife] and may not divorce her until he had attained [legal] age. '[In respect] of halizah'  — to exclude [the ruling] of R. Jose who said, 'In the [Biblical] section [of halizah] it is written, Man;  but [in the case of] a woman there is no difference between a major and a minor';  hence it was necessary to teach us that 'woman' is compared to 'man', contrary to [the view of] R. Jose. 'And [in respect of declarations of] refusal', [this had to be mentioned] in order to exclude [the ruling] of R. Judah who said: [A girl can exercise the right of refusal] until the black  predominates;  hence it was necessary to teach us that [the law is] not in accordance with [the view of] R. Judah.  'And [in respect of] the sale of the estate of his father, until he becomes twenty years of age' [had to be taught] in order to exclude [the view] of him who said [the youth need only be] eighteen years of age. The law [is that during the] 'intervening period'  [one is regarded] as being under age.  The law [is] in accordance with Giddal b. Menashya.  The law [is] in accordance with Mar Zutra.  The law is according to Amemar.  And the law is in accordance with [what] R. Nahman said in the name of Samuel, in all [cases]. MISHNAH. IF [A PERSON] DISTRIBUTED HIS POSSESSIONS VERBALLY, R. ELEAZAR  SAID, WHETHER HE WAS IN GOOD HEALTH OR DANGEROUSLY ILL, [ALL] REAL ESTATE  IS ACQUIRED BY MEANS OF MONEY,  DEED  AND POSSESSION,  WHILE MOVABLE OBJECTS  ARE ONLY ACQUIRED BY MEANS OF PULLING.