Midrash for Genesis 4:14

"You shall be aware," etc., R. Juda b. Chiya said: "Infer [from the verse cited in the Mishnah) that Cain made wounds and bruises on the body of his brother Abel, as he did not know by what member the soul departed until he reached his neck." R. Juda said again in the name of R. Chiya: "From the very day when the earth opened its mouth to receive the blood of Abel, it has not again opened, as it is said (Is. 24, 16) Frum the edge of the earth, etc. Hence it reads from the edge, but not from the mouth. Hezekiah, his brother, however, raised the following objection (Num. 26, 32) And the earth opened her mouth, etc. And he answered: "It opened for a bad cause, but not for a good cause." R. Juda said again in the name of R. Chiya: "Exile atones for every thing, for it is said (Ib. (Gen. 6, 14) And I shall be a fugitive and a vagabond on the earth, and at last it is written: And he dwelt in the land of Nod (only a vagabond)."

R. Alexandri said in the name of R. Chiya b. Abba: "The miracle that is done for a sick person is much greater than the miracle wrought unto Chanania, Mishael and Azariah; for, at the miracle of Chanania, Mishael and Azariah it was an ordinary lire that could be quenched by all; but the fire that is within a sick person is a heavenly fire and can not be quenched." A. Alexandria said further in the name of R. Chiya b. Abba, according to others in the name of R. Joshua b. Levi: "As soon as the end of a man approaches, everything rules over him, as it is said (Gen. 4, 14) It will come to pass that everyone who findeth me will slay me." Raba said that we infer it from the following (Ps. 119, 91) They stand this day according to Thine ordinances; for all things are Thy servants. The Rabbis related to Rabba b. Shila that a certain tall man died while riding on a little mule, and as he approached the bridge the mule became wild and threw him off into the river, which caused his death. Rabba b. Shila applied to that man the above-quoted passage. They stand, this day, etc. Samuel saw how a snake was carried upon the back of a frog to enable it to pass a stream and bit a person who died of the bite. Samuel applied to that man the above quoted passage. They stand, etc.

Behold, Thou hast driven me out this day from the face of the land … and the Lord said unto him: “Therefore, whosoever slayeth Cain, vengeance shall be taken on him sevenfold.” and the Lord set a sign for Cain (Gen. 4:14–15). There are some who say that the word “Sabbath” was placed as a sign upon his countenance, as it is said: My Sabbaths, for it is the sign between Me and you, throughout your generations (Exod. 31:13), and that just as the Sabbath pleaded in behalf of Adam,³⁵The Sabbath pleaded with God to spare Adam’s life lest the glory and the sanctity of the Sabbath be impaired by his death. it pleaded in behalf of Cain. Others, however, insist that He fastened a horn upon his forehead.³⁶Bereshit Rabbah lists seven signs placed on Cain.