A prominent haggadist of the fourth amoraic generation (fourth century), contemporary of Judah (Judan) b. Simon (b. Pazzi; Midr. Teh. to viii. 2, cxiii. 1). He was versed in the Halakah, in which he often reported opinions in behalf of Rabbi Yannai (Ket. 54b, 104b; ḳid. 19a, 33a; Zeb. 103a); but no original decisions have come down from him. In the field of the Haggadah, on the contrary, while we find him repeating observations of his predecessors (Gen. R. xliv., lxxxii.; Midr. Teh. to ci. 8), he is generally original in his remarks. Commenting on Jacob's order to Joseph, "Go and see whether it be well with thy brethren and well with the flock" (Gen. xxxvii. 14), the question is raised, Do flocks of sheep appreciate human greetings? Whereunto Aibu replies: "It is man's duty to pray for and look after the well-being of the dumb animal that contributes to his welfare" (Tan., Wayesheb, 13, ed. Buber; see Gen. R. lxxxiv.). In specifying the number of men that escorted Abraham on his journey to Moriah (Gen. xxii. 3), and Saul on his visit to the witch of En-dor (I Sam. xxviii. 8), Scripture, according to R. Aibu, intends to convey the practical lesson, that man when traveling should be accompanied by at least two servants, or else he may himself become his servant's servant (Lev. R. xxvi.).
In his Biblical exegesis, he aims to reconcile variations in Scriptural expressions. Thus, Aibu explains the reason assigned for God's mercies in the passage, "The Lord will not forsake his people for his great name's sake" (I Sam. xii. 22), and the omission of that reason in the similar message, "The Lord will not cast off his people" (Ps. xciv. 14), by applying the latter to the times of the people's piety, and the former to the days of heedlessness. God is always good: when the people are deserving of His goodness He showers it upon them for their own sake; when, on the contrary, they are not deserving, He forsakes them not for His great name's sake (Ruth R. to i. 6). Similarly, he explains the variation in the version of the Fourth Commandment, "Remember the Sabbath day" (Ex. xx. 8), and "Keep the Sabbath day" (Deut. v. 12). According to Aibu (on behalf of Resh LaḲish) the term "remember" applies to cases when one is not able to rest on the Sabbath day, as, for instance, when one is on a sea voyage, and only remembering is possible; the term "keep" applies to ordinary circumstances, when "keeping" is obligatory (PesiḲ. R. xxiii.).
Dwelling on the verse (Ps. viii. 4 [A. V. 3]), "When I consider thy heavens, the work of thy fingers," etc., Aibu remarks:
"There are three classes of men: (1) those who are contented with admiring the grandeur of the sky, with the moon and stars and planets; (2) those who pray to God to reserve all the good due to them for heaven in the hereafter; and (3) a class of lazy workingmen who say, 'Whatever thou wilt give us, give us now, both what may be our due and whatever may be bestowed upon us through our fathers' merits: give us whatever thy fingers have wrought'" (Midr. Teh. to Ps. viii. 4).
Elsewhere he says: "No man departs from this world having realized even half of his desires. When a man has acquired a hundred pieces of gold, he longs to increase them to two hundred; and when he has two hundred, he is anxious to double these again" (Eccl. R. i. 13, iii. 10). Aibu's homiletic observations are numerous, both those related in his own name and those reported in his behalf by the haggadists of his own and subsequent generations (compare PesiḲ. i., iii., v., xvii., xxv., xxvii.; PesiḲ. R. ed. Friedman, index; Tan., ed. Buber, index; Midr. Teh. ed. Buber, index; Bacher, "Ag. Pal. Amor." iii. 63-79).