What were the three main principles of Saint Benedictine’s Rule in the 400's A.D.?

Answer 1

1. Stability (to live in one monastery for life)
2. Obedience (to all lawful authority)
3. Conversion of Manner (this one includes many things including chastity, poverty, etc.)

These are the vows that a Benedictine takes, which are slightly different, as you can see, from what other Religious Order use.

Here is a link if you wish to learn more.
http://www.osb.org/rb/index.html

Answer 2

The renunciation of one's own will; obedience to Christ and one's monastic superiors; and salvation through perseverance in the monastic life and by sharing in the passion of Christ.

Answer 3

There were more than three. They can probably be summed up by peace, prayer, and work.

Answer 4

1. Concerning the Kinds of Monks and Their Manner of Living.

It is manifest that there are four kinds of monks. The cenobites are the first kind; that is, those living in a monastery, serving under a rule or an abbot. Then the second kind is that of the anchorites; that is, the hermits-those who, not by the new fervour of a conversion but by the long probation of life in a monastery, have learned to fight against the devil, having already been taught by the solace of many. They, having been well prepared in the army of brothers for the solitary fight of the hermit, being secure now without the consolation of another, are able, God helping them, to fight with their own hand or arm against the vices of the flesh or of their thoughts.
But a third very bad kind of monks are the sarabaites, approved by no rule, experience being their teacher, as with the gold which is tried in the furnace. But, softened after the manner of lead, keeping faith with the world by their works, they are known through their tonsure to lie to God. These being shut up by twos or threes, or, indeed, alone, without a shepherd, not in the Lord's but in their own sheep-folds-their law is the satisfaction of their desires. For whatever they think good or choice, this they call holy; and what they do not wish, this they consider unlawful. But the fourth kind of we are about to found, therefore, a school for the monks is the kind which is called gyratory. During their whole life they are guests, for three or four days at a time, in the cells of the different monasteries, throughout the various provinces; always wandering and never stationary, given over to the service of their own pleasures and the joys of the palate, and in every way worse than the sarabaites. Concerning the most wretched way of living of all such monks it is better to be silent than to speak. These things therefore being omitted, let us proceed, with the aid of God, to treat of the best kind, the cenobites.

2. What the Abbot Should Be Like

. An abbot who is worthy to preside over a monastery ought always to remember what he is called, and carry out with his deeds the name of a Superior. For he is believed to be Christ's representative, since he is called by His name, the apostle saying: "Ye have received the spirit of adoption of sons, whereby we call Abba, Father." And so the abbot should not-grant that he may not-teach, or decree, or order, any thing apart from the precept of the Lord; but his order or teaching should be sprinkled with the ferment of divine justice in the minds of his disciples. Let the abbot always be mindful that, at the tremendous judgment of God, both things will be weighed in the balance: his teaching and the obedience of his disciples. And let the abbot know that whatever the father of the family finds of less utility among the sheep is laid to the fault of the shepherd. Only in a case where the whole diligence of their pastor shall have been bestowed on an unruly and disobedient flock, and his whole care given to their morbid actions, shall that pastor, absolved in the judgment of the Lord, be free to say to the Lord with the prophet: "I have not hid Thy righteousness within my heart, I have declared Thy faithfulness and Thy salvation, but they despising have scorned me." And then at length let the punishment for the disobedient sheep under his care be death itself prevailing against them. Therefore, when any one receives the name of abbot, he ought to rule over his disciples with a double teaching; that is, let him show forth all good and holy things by deeds more than by words. So that to ready disciples he may propound the mandates of God in words; but, to the hard-hearted and the more simpleminded, he may show forth the divine precepts by his deeds. But as to all the things that he has taught to his disciples to be wrong, he shall show by his deeds that they are not to be done; lest, preaching to others, he himself shall be found worthy of blame, and lest God may say at some time to him a sinner: "What hast thou to do to declare my statutes or that thou should'st take my covenant in thy mouth. Seeing that thou hatest instruction and casteth my words behind thee; and why beholdest thou the mote that is in thy brother's eye, but considerest not the beam that is in thine own eye?" He shall make no distinction of persons in the monastery. One shall not be more cherished than another, unless it be the one whom he finds excelling in good works or in obedience. A free-born man shall not be preferred to one coming from servitude, unless there be some other reasonable cause. But if, justice demanding that it should be thus, it seems good to the abbot, he shall do this no matter what the rank shall be. But otherwise they shall keep their own places; for whether we be bond or free we are all one in Christ; and, under one God, we perform an equal service of subjection; for God is no respecter of persons. Only in this way is a distinction made by Him concerning us: if we are found humble and surpassing others in good works. Therefore let him (the abbot) have equal charity for all: let the same discipline be administered in all cases according to merit. In his teaching indeed the abbot ought always to observe that form laid down by the apostle when he says: "reprove, rebuke, exhort." That is, mixing seasons with seasons, blandishments with terrors, let him display the feeling of a severe yet devoted master. He should, namely, rebuke more severely the unruly and the turbulent. The obedient, moreover, and the gentle and the patient, he should exhort, that they may progress to higher things. But the negligent and scorners, we warn him to admonish and reprove....

3. About Calling in the Brethren to Take Council
As often as anything especial is to be done in the monastery, the abbot shall call together the whole congregation, and shall himself explain the question at issue. And, having heard the advice of the brethren, he shall think it over by himself, and shall do what he considers most advantageous. .

4. What are the Instrument of Good Works

5. Concerning Obedience
. The first grade of humility is obedience without delay. This becomes those who, on account of the holy service which they have professed, or on account of the fear of hell or the glory of eternal life, consider nothing dearer to them than Christ: so that, so soon as anything is commanded by their superior, they may not know how to suffer delay in doing it, even as if it were a divine command. Concerning whom the Lord said: "As soon as he heard of me he obeyed me."

http://www.fordham.edu/halsall/source/rul-benedict.html