After his ordination he declined a teacher's position, recommending in his stead a more needy friend, R. Abba of Acre (Acco), as worthier than himself (Sotah, 40a). He thereby illustrated his own doctrine that it is a divine virtue to sympathize with a friend in his troubles as well as to partake of his joys (Tan., Wa-yesheb, ed. Buber, 16). Later he assumed the office of rector in Cæsarea, the former seat of R. Hoshaya I, and established himself at the so-called Kenishta Maradta (Insurrectionary Synagogue; Yer. Nazir vii.56a; Yer. San. i.18a; compare Josephus, B. J. ii.14, § 5; Jastrow, Dict. p. 838), whence some of the most prominent teachers of the next generation issued. He did not, however, confine his activity to Cæsarea, where he originated several ritualistic rules (Yer. Demai ii.23a, R.H. 34a), one of which—that regulating the sounding of the shofar—has since been universally adopted, and is referred to by medieval Jewish casuists as "Takkanat R. Abbahu" (the Enactment of R. Abbahu; compare "Maḥzor Vitry," Berlin, 1893, p. 355). He also visited and taught in many other Jewish towns (Yer. Berakhot viii.12a; Yer. Shab. iii.5c).
While on these journeys, Abbahu gathered so many Halakot that scholars turned to him for information on mooted questions (Yer. Shabbat viii.11a; Yer. Yevamot i.2d). In the course of these travels he made a point of complying with all local enactments, even where such compliance laid him open to the charge of inconsistency (Yer. Berakhot viii.12a; Yer. Beitzah, i.60d). On the other hand, where circumstances required it, he did not spare even the princes of his people (Yer. Avodah Zarah, i.39b). Where, however, the rigorous exposition of laws worked hardship on the masses, he did not scruple to modify the decisions of his colleagues for the benefit of the community (Shabbat 134b; Yer. Shabbat xvii.16b; Yer. Mo'ed Katan i.80b). As for himself, he was very strict in the observance of the laws. On one occasion he ordered some Samaritan wine, but subsequently learning that there were no longer any strict observers of the dietary laws among the Samaritans, with the assistance of his colleagues, Ḥiyya b. Abba, Rav Ammi, and Rav Assi, he investigated the report, and, ascertaining it to be well founded, did not hesitate to declare the Samaritans, for all ritualistic purposes, Gentiles (Yer. Avodah Zarah, v. 44d; Hullin 6a).
Let man ever be of the persecuted, and not of the persecutors; for there are none among the birds more persecuted than turtle-doves and pigeons, and the Scriptures declare them worthy of the altar.|10|10|Bava Kamma 93a
R. Abbahu, though eminent as a halakist, was more distinguished as a haggadist and controversialist. He had many interesting disputes with the Christians of his day (Shab. 152b; San. 39a; Av. Zarah, 4a). Sometimes these disputes were of a jocular nature. Thus, a heretic bearing the name of Sason (=Joy) once remarked to him, "In the next world your people will have to draw water for me; for thus it is written in the Bible (Isaiah 12:3), 'With joy shall ye draw water.'" To this R. Abbahu replied, "Had the Bible said 'for joy' [le-sason], it would mean as thou sayest, but since it says 'with joy' [be-sason], it means that we shall make bottles of thy hide and fill them with water" (Suk. 48b). These controversies, though forced on him, provoked resentment, and it is even related that his physician, Jacob the Schismatic (Minaah), was slowly poisoning him, but R. Ammi and R. Assi discovered the crime in time (Av. Zarah, 28a).
Abbahu had two sons, Zeira and Ḥanina. Some writers ascribe to him a third son, Abimi (Bacher, Ag. Pal. Amor.). Abbahu sent Ḥanina to the academy at Tiberias, where he himself had studied, but the lad occupied himself with the burial of the dead, and on hearing of this, the father sent him a reproachful message in this laconic style: "Is it because there are no graves in Cæsarea (compare Exodus 14:11) that I have sent thee off to Tiberias? Study must precede practice" (Yer. Pesahim iii.30b). Abbahu left behind him a number of disciples, the most prominent among whom were the leaders of the 4th amoraic generation, R. Jonah and R. Jose. At Abbahu's death the mourning was so great that it was said, "Even the statues of Cæsarea shed tears" (Mo'ed Katan 25b; Yer. Av. Zarah, iii.42c).
Abbahu made a notable exception with reference to the Tosefta's statement that the Gilionim (Evangels) and other books of the Mineans are not to be saved from a conflagration on Sabbath: "the books of those at Abidan may be saved" (Shab. 116a). Of special historical interest is the observation of Abbahu in regard to the benediction "Baruk Shem Kebod Malkuto" (Blessed be the Name of His glorious Kingdom) after the "Shema' Yisrael," that in Palestine, where the Christians look for points of controversy, the words should be recited aloud (lest the Jews be accused of tampering with the unity of God proclaimed in the Shema'), whereas in the Babylonian city of Nehardea, where there are no Christians, the words are recited with a low voice (Pesahim 56a). Preaching directly against the Christian dogma, Abbahu says: "A king of flesh and blood may have a father, a brother, or a son to share in or dispute his sovereignty, but the Lord saith, 'I am the Lord thy God! I am the first; that is, I have no father, and I am the last; that is, I have no brother, and besides me there is no God; that is, I have no son'" (Isaiah 44:6; Ex. R. 29). His comment on Numbers 23:19 has a still more polemical tone: "God is not a man that he should lie; neither the son of man, that he should repent. If a man say, 'I am God,' he lieth, and if he say, 'I am the son of man,' he will have to repent, and if he say, 'I shall go up to heaven,' he will not do it, nor achieve what he promises" (Yer. Ta'anit, ii.65b).
Some of his controversies on Christian theological subjects, as on Adam (Yalḳ., Gen. 47), on Enoch (Gen. R. 25), and on the resurrection (Shab. 152b), are less clear and direct (see Bacher, Ag. Pal. Amor. ii.97, 115-118).