Since the purpose of the work was to educate the general public to religious ways and true faith against the historical background of his time and events, the commentary is of great importance in revealing the problems facing his generation in the various spheres of faith and knowledge. Thus, for instance, in choosing what he determined to be the correct approach to the question of belief in the Messiah and the attitude to be taken to secular studies, the Author at the same time takes note of the prevailing conditions and attempts to better them. It would seem, therefore, that the purpose of his work was identical with that of his communal and halakhic activity—to lead and reshape his generation in the right way, as he viewed it in the light of his experience. Despite his strong and decisive personality, R. Jacob's work reveals his humility and his care not to impose his way upon others, whether the scholars of the original community (the Romaniot) or his Spanish contemporaries. R. Jacob declared that from the time he began this work he withdrew from all his communal activity, and apparently from 1514 he devoted himself to his work, the first part of which was published in 1516. The Ein Ya'akov has been published in more than 100 editions and scores of commentaries have been written on it. Changes have taken place since the first edition, as a result of Christian censorship, and in order to adjust the text of passages to that in the standard edition of the Talmud. Although designed as a work for broad and popular circles, it is extensively used by scholars.

R. Jacob b. Shlomo ibn Habib (?1445–1515/16), was born in Zamora in Castile, Spain, where he is said to have been a pupil of R. Samuel Valency, and was one of the renowned scholars of Castile, heading a yeshivah in Salamanca which was one of the largest in Spain. On the expulsion of the Jews from Spain in 1492 he went to Portugal and before 1501 proceeded to Salonika where he became one of the leading scholars. First he taught in the Calabrian (native) community, and later was appointed rabbi of the Gerush community (of Spanish exiles), a position which he held until his death. His name appears among the first signatories on the early regulations of Salonika. He was personally responsible for some of these regulations, which would even seem to have been formulated by him. He also conducted a yeshivah in Salonika. His contemporaries and successors spoke of him in terms of the highest esteem and referred to him as gedol ha-dor ("the greatest of the generation"), mofet ha-dor ("the wonder of the generation"), and ha-ga'on. Individual responsa by him have been preserved in the works of contemporary and later scholars (R. Elijah Mizrahi, R. Samuel de Medina, and in the collection of responsa Zera Anashim (1902), while others exist in manuscript. He is quoted at length in the works of the great scholars of the period (R. David b. Hayyim ha-Kohen of Corfu, R. Joseph Caro, R. Joseph ibn Lev, and others). Remnants of his halakhic works have also been preserved. In his Beit Yosef, R. Joseph Caro gives quotations from R. Jacob's commentary on the beginning of Orah Hayyim and the beginning of Yoreh De'ah of the Arba'ah Turim. R. Samuel de Medina in his responsa (YD, 44) gives a synopsis of his article on the law of terefah, and there are references to disputes between him and his contemporaries on halakhic topics. His extant responsa show his special concern with the problems that occupied the generation after the expulsion—such as the case of a childless widow whose brother-in-law, from whom she had to receive halizah, had become converted to Christianity—as well as the new problems which had arisen as a result of the settling of the Jews of Spain in places where the religious customs (minhag) differed from those in vogue in Spain. R. Jacob took up a tolerant attitude toward the customs of these communities and their scholars and accepted compromises, instead of forcing his views upon them, as did the scholars of the following generation. He states explicitly that he had not studied philosophy and the sciences methodically, although he had occupied himself with these subjects in his youth. His knowledge of Kabbalah, toward which he took a positive attitude, was also the result of casual reading.

עם הקדמות המחבר, מהרש"א, הרי"ף ור' יצחק מאיר פרנקל והשירים של ר' יעקב יוזביל ור' יהודה אריה ממודינא לכבוד הרי"ף וספרו מאור עינים (דף קעח, ב), שהועתקו מדפוס אמשטרדם תמ"ד. "כל אגדות הירושלמי" מתוך "יפה מראה" הנז' בשער לא נדפסו, אלא שבתוך פירוש "הכותב" למאמרי הירושלמי שבסוף חלק א נוספו בסוגריים קטעים מתוך "יפה מראה". ר' יצחק מאיר פרנקיל-[תאומים] כותב בהקדמתו: "אמרתי ... לאסף ... ולדפוס ספר עין ישראל ... בתוספת מרובה ... בשם כתנות אור ... לחקוק בעט ברזל ועופרת ספרי אמ"ו (מוהר"ר יונה) זלה"ה (תאומים)" והוסיף חידושים שלו "אגב עמהם". המגיה, ר' שלמה זלמן, הוסיף הגהות והערות משלו, אך מאידך קיצר והשמיט בכמה מקומות בסוף פירושי המחבר "אמר הכותב". [שמא ההוספות וההשמטות הן של ר' יצחק מאיר?]. בהסכמתו של ר' נפתלי הכהן נאמר: "כבר נתתי הסכמה ... להדפיס העין יעקב גדולים ... להאלוף זעליגמן רייש מקהלתינו ק"ק פרנקבורט [דמיין] ... אמנם כן שמעתי שכבוד האלוף הר"ר הענך מק"ק פרנקבורט דאדרא מתעסק כבר בהדפסת הספר ... באמצע המלאכה ... בכן בטלתי עתה דעתי ונכנסתי ... לפייס את האנשים אשר התחילו להתעסק במלאכה זו ולכבודי נתפייסו".

הסכמות: ר' דוד ב"ר אברהם אופנהיים מפראג, ווינא, כו אלול תס"ז; - חלק א ר' נפתלי הכהן, פרנקבורט דמיין, כו שבט תס"ח; - חלק א ר' גבריאל ב"ר יהודא ליב [עשקעלעס] מקראקא, נ"ש (ניקלשפורג), י אייר תס"ז; - חלק א ר' יששכר בערמן ב"ר דוד יצחק זעקיל סג"ל [פרענקיל], פירדא "ורובץ תחת משא בני מדינות אנשבך וק"ק שנייטך", א דראש-חודש אדר תס"ח; - חלק א ר' שמעי' ב"ר אברהם יששכר בער מברלין, "פרנקפורט ביומא דשוקא", כב [צ"ל: כד] אדר תס"ח; - חלק א ר' אהרן ב"ר יצחק בנימן וואלף, ברלין "ומצ"פ בק"ק פרנקפורט דאדר", ערב ראש-חודש אב תס"ט; - חלק א ר' יהודא אריה ליב, אמשטרדם, ו אב תס"ח; - חלק א דייני אמשטרדם: ר' יהודא ליב ב"ר אפרים אשר אנשיל המבורג שפץ , ר' יצחק ב"ר שלמה מזאמשטש, ר' יוסף ב"ר ראובן יהודא כ"ץ ור' פנחס זעליג ב"ר משה, "זעירא דחברייא דבני ישיבה דק"ק פוזנן ... ספרא ודיינא דק"ק אמשטרדם", ערב ראש-חודש מרחשון תס"ח. - חלק א ב: ר' יהודא ליב ב"ר משה, גלוגא רבתי, לו למב"י [כא אייר] תס"ח; - [חלק ב] ר' אברהם מרדכי ב"ר ישראל היילפרן מוואלטש, פרנקפורט דאדר, כד תמוז תס"ז; - [חלק ב] ר' סעדישעיה [סעדיה ישעיה] ב"ר שאול לבית קצנאילנבוגין, מעזריטש, בא תס"ח; - [חלק ב] רבני פוזנן: ר' שמואל זנבל ב"ר חנוך, ר' יצחק ב"ר מאיר "פרנס ראשון וב"י [ונאמן בית ישראל]", ר' פלק ב"ר מאיר דרשן ור' יעקב ב"ר מאיר "דיין וב"י", טז שבט תס"ח. - [חלק ב]