Abraham married three wives--Sarah, a daughter of Shem; Keturah, a daughter of Japheth; and Hagar, a daughter of Ham.
Rashi supposes that Keturah was one and the same with Hagar--so the Midrash, the Targum Yerushalmi, and that of Jonathan. The latter says, "Keturah, she is Hagar, who had been bound to him from the beginning," but Aben Ezra and most of the commentators contend that Keturah and Hagar are two distinct persons, and the use of the plural concubines, in verse 6, bears them out in this assertion.
The Holy One--blessed be He!--daily proclaims a new law in the heavenly court, and even all these were known to Abraham.
A Gentile once asked Rabbi Yoshua ben Kapara, "Is it true that ye say your God sees the future?" "Yes," was the reply. "Then how is it that it is written (Gen. vi. 6), 'And it grieved Him at His heart'?" "Hast thou," replied the Rabbi, "ever had a boy born to thee?" "Yes," said the Gentile; "and I rejoiced and made others rejoice with me." "Didst thou not know that he would eventually die?" asked the Rabbi. "Yes," answered the other; "but at the time of joy is joy, and at the time of mourning, mourning." "So it is before the Holy One--blessed be He!--seven days He mourned before the deluge destroyed the world."
All the strength of the soul's mourning is from the third to the thirtieth day, during which time she sits on the grave, still thinking her beloved might yet return (to the body whence she departed). When she notices that the color of the face is changed, she leaves and goes away; and this is what is written (Job. xiv. 22), "But his flesh upon him shall have pain, and his soul shall mourn over him." Then the mouth and the belly quarrel with one another, the former saying to the latter, "All I have robbed and taken by violence I deposited in thee;" and the latter, having burst three days after its burial, saying to the former, "There is all thou hast robbed and taken by violence! as it is written (Eccles. xii. 6), 'The pitcher is broken at the fountain.'"
Job said, "Even the devil shall not dissuade me from comforting those that mourn; for I would tell him that I am not better than my Creator, who comforts Israel; as it is said (Isa. li. 12), 'I, even I, am He that comforteth you.'"