Bava Batra

but [if the act is] not [done] in his presence, he must say, Go, occupy and acquire ownership. Rab inquired: What is the rule in the case of a gift? Said Samuel: What is Abba's  difficulty? Seeing that in the case of a sale where the purchaser gives money, if the seller says to him, 'Go, occupy and acquire ownership,' he does acquire ownership but otherwise not, how much more so in the case of a gift?  — Rab, however, was of opinion that a gift is usually made in a liberal spirit. How much is meant by 'anything at all'? — [The answer is given] in the dictum of Samuel: If a man raises a fence already existing to ten handbreadths  or widens an opening so that it allows of entry and exit, this constitutes effective occupation.  How are we to picture this fence? If we say that before [the man touched it] people could not climb it and now too they cannot climb it, what has he done?  If again we say that before people could climb it but now they cannot, he has done a great deal!  — We must therefore say that before it could be climbed easily but now it can only be climbed with difficulty. How are we to picture the opening? If we say that before people could get through it and now too they can get through it, what has he done?  If again we say that before people could not get through it but now they can, he has done a great deal!  We must therefore say that before people got through with difficulty, but now they get through easily. R. Assi said in the name of R. Johanan: If [in the estate of a deceased proselyte] a man by placing a pebble or removing a pebble confers some advantage, this action gives him a title to the land. How are we to understand this placing and removing? If we say that by placing the pebble [there] he stops water from overflowing the field  or by removing the pebble he allows water to run off from the field,  he is merely in the position of 'a man who chases a lion from his neighbour's field'!  — We must say therefore that in placing the pebble he conserves the water  and in removing the pebble he makes a passage for the water. R. Assi further said in the name of R. Johanan: [If the estate of a deceased proselyte consists of] two [adjacent] fields with a boundary between them, then if a man takes possession  of one of them with the idea of becoming owner, he acquires ownership of that one;