ויהי הבל רועה צאן, Hevel chose this vocation as it required more intelligence and involved one’s mental activities more that farming.

וקין היה עובד אדמה, as a result of each having his own vocation, they each brought different offerings to G’d.

To Hevel and to his offering. Hashem was pleased with both Hevel himself as well as with his offering.

ואל קין ואל מנחתו לא שעה, He did not turn to Kayin the donor, as he was not pleasing in the eyes of G’d; He also did not turn with favour to his offering seeing the nature of the offering was not designed to make it welcome;

ויחר, due to his jealousy of his brother,

ויפלו פניו, he was downcast, being ashamed, feeling that G’d had publicly shamed him.

Why are you angry. Why are you jealous that I accepted your brother’s offering? I did not do so arbitrarily nor was it unjust.

Why are you depressed. It is pointless to brood over the past when the matter can be rectified

הלא אם תיטיב, if only you improve yourself you will also be welcome in My eyes.

שאת, every lofty level of greatness is lying in wait for you, ready to become yours,

ואם לא תיטיב לפתח חטאת רובץ, however, sin is also lying in wait for you if you will add further intentional sin to the already performed unintentional sin. This is the way of the evil urge, that once you give into it, it will forever be ready to tempt you again.

כי אליך תשוקתו, “for it longs for you due to its very nature. It too is anxious to satisfy its desires, its aspirations every day.”

ואתה תמשול בו, it is within your power to overcome the power of the evil urge thanks to the צלם אלוקים, the divine image with which you have been provided at birth. This conforms to our sages in Sukkah 52 who have taught that were it not for this צלם אלוקים, which represents G’d’s assistance against the evil urge, there would be no way man could cope with temptation. This is what David meant in Psalms 37,33 ה' לא יעזבנו בידו ולא ירשיענו בהשפטו, “the Lord will not abandon him to his power; He will not let him be condemned in judgment.”

ויאמר קין אל הבל אחיו, how upset he was, and how he had become downcast on account of his brother.

ויהי בהיותם בשדה, away from the presence of their parents.

ויקם קין, Kayin arose without any previous quarrel, similar to Deuteronomy 19,11 וארב לו וקם עליו, “he ambushed him and attacked him.”

אי הבל אחיך, “in which place did you bury him?” G’d phrased this as a question only in order to give Kayin a chance to begin the process of repentance, not because He was not perfectly aware where Kayin had buried Hevel. G’d did not want to be forced to kill someone already guilty of the death penalty.

לא ידעתי, “I do not know.” He thought that the question concerned Hevel’s whereabouts. Seeing that Kayin had not been interested previously in G’d’s ability to know the future, or to become close to Him; such knowledge about G’d was reserved to those who are cleaving to Him.

ארור אתה מן האדמה, cursed and deprived of the good the earth has to offer.

אשר פצתה את פיה, because it allowed itself to be used to cover up the killing of your brother. As a result, earth will no longer be free to provide the needs of your livelihood in the degree it did up until now. There was no need to spell out the penalty for the murderer. His punishment is part of the principle applying to the penalty for anyone causing willful damage, i.e. he will experience tit for tat as spelled out in Leviticus 24,19.

גדול עוני מנשוא, after Kayin finally realised how G’d in Heaven supervises every detail which goes on down on earth, he was convinced that G’d must know that his sole motivation in doing repentance was to escape punishment. Even this type of repentance was wrung from him only after G’d had pressured him to display penitence. He was embittered, and this is what prompted him to exclaim that the severity of his sin was such there was no hope to obtain forgiveness which would protect him against retribution in kind. The matter is similar to Saul’s failure in killing Agag, King of Amalek. Saul had said to Samuel: “I have sinned,” only after Samuel had insisted that he make a confession of having failed to carry out G’d’s instructions. (Samuel I 15,24) Samuel had had to tell Saul that G’d had despised him as a future leader of the Jewish people before he could prevail on Saul to acknowledge his wrongdoing. (Samuel I 15,24)

והיה כל מוצאי יהרגני, the fact that anyone who finds me is legally entitled to kill me makes my punishment much more severe than You, G’d, have told me.

כל הורג קין שבעתים יוקם, I, G’d, announce that anyone who dares to kill Kayin, [i.e. who takes the law into his own hands, Ed.] would be punished seven more times than what the crime he committed appears to warrant. Anyone who is prepared to kill someone is called הורג, as for instance, in Hoseah 9,13 ואפרים להוציא אל הורג בניו, “Ephrayim too must bring out his children to his slayers.” The word שבעתים means “twice seven times,” as in Proverbs 6,31 ונמצא ישלם שבעתים, “when he is found out he must pay twice sevenfold.” G’d decreed therefore that when someone killed half the human race, or at least a third of the human race, the appropriate vengeance would involve a twice sevenfold penalty. This would manifest itself in such a slayer being a restless wanderer on earth for seven generations. Such a life is considered worse than death. When David prays in Psalms 59,12אל תהרגם פן ישכחו עמי הניעמו בחילך, “do not kill them lest my people will forget them; make them wanderers seeing it is in Your power,” he meant that they be killed only at the end of seven generations. David wanted the punishment of his enemies to last. If they would all die and disappear at once their absence would soon be forgotten. Kayin got his deserts at the end of seven generations as we know from traditional sources in Tanchuma 10.

שמען קולי נשי למך, Lemech called out in grief

אמרתי, I have to express my mental anguish’

הרגתי לפצעי, I have caused myself real injury, for the one who has killed my father (ancestor Kayin) has inflicted upon me the child a deep wound, seeing that the killer was my son.

ולמך שבעים ושבעה. My anguish over what I have done will be many times greater than the anguish of Kayin who had been condemned to be a constant fugitive on the earth. 'כי שבעתים יוקם קין וגו, for if Kayin’s punishment was indeed great, my punishment for having killed my son will be many times greater. [he referred to the anguish he suffered over what he had done, not to the punishment imposed upon him externally, as retribution. Ed.]

אז הוחל לקרא בשם ה, at that time the righteous people of the earth began to preach monotheism to the public. The meaning is similar to Genesis 21,33 ויקרא שם בשם ה' א-ל עולם, “Avraham proclaimed there the name of the Lord, the Lord of the universe.” The time had come to publicly confront and refute the arguments of the idolaters in that period.