Question: Shnayim mikra ve-echad targum is a Halacha that commands that a person, in addition to listening to the Torah portion being read in the synagogue, read it themselves twice during the week, along with a translation. Can I read the Parsha in English? Is it acceptable to use an English translation instead of Targum Onkelos? What about using Rashi as a translation?
Answer: The Gemara in Brachos (8a) teaches that one should complete the weekly Torah portion twice ("shnayim mikra") and its translation once ("echad targum"). The Gemara promises that fulfilling this practice will result in the reward of extended days and years. This obligation is codified in the Shulchan Aruch (285:1), which states, "One is obligated in Shnayim Mikra V'Echad Targum."
The Aruch Hashulchan (285:2) explains that this halacha dates back to the time of Moshe Rabbeinu. When he instituted the Torah readings on Monday, Thursday, and Shabbos (Rambam: Tefillah 12:1), he also established that one should read Shnayim Mikra V'Echad Targum.
Even if one does not understand the Hebrew text of the Parsha, he still fulfills the obligation by reading it (Chut Shani: Shabbos 4:27:2:4). However, if the Parsha is read in English, one does not fulfill the obligation.
Regarding the translation, "targum" in the Gemara refers to Targum Onkelos. This means that the fundamental obligation is to read the Torah portion twice in Hebrew and the translation of Onkelos once.
There is a dispute in the Sefer Mitzvos Gadol (SMa" G, Positive Mitzvah 19) regarding whether one can use a commentary (such as Rashi) in place of Onkelos. The Mishnah Berurah (285:6) explains that Onkelos has the advantage of being transmitted at Sinai (Megillah 3a), and it translates every word of the Torah. Rashi, on the other hand, provides explanations based on the teachings of Chazal, making it a more comprehensive understanding of the verses.
The Shulchan Aruch (285:2) rules that Rashi is an acceptable substitute for Onkelos. (The Mishnah Berurah (285:5) says that the individual should read the verse three times if a verse does not have Rashi's commentary.) However, the Shulchan Aruch continues that someone who fears Heaven should ideally read Rashi and Onkelos to benefit from both.
In Shemiras Shabbos KeHilchasa (42:215), it is written that even if one does not fully understand the Targum, he must still read it as part of Shnayim Mikra.
As for using a different translation besides Rashi or Onkelos, the Mishnah Berurah (285:4) rules that literal translations are insufficient because they do not capture the broader meanings conveyed by Chazal. The Mishnah Berurah (285:5) allows individuals who do not understand Rashi to read other explanations, such as Tz'enah Ur'enah (a Yiddish translation).
Regarding an English translation, Teshuvos VeHanhagos (1:261) responds to a Baal Teshuvah that, since he cannot understand Rashi or Onkelos at all, he may read the Torah twice in Hebrew and the Targum in English. However, he cautions, as the Mishnah Berurah does, that translations must reflect the teachings of Chazal rather than be literal translations.
Rav Moshe Feinstein is quoted in Yagel Yaakov (Dardak, p. 298) as permitting an individual who does not understand Rashi well to read the Hebrew text twice and use an English translation of Rashi for the Targum.
In short, The obligation of Shnayim Mikra V'Echad Targum dates back to the time of Moshe Rabbeinu, with the Gemara promising a long life for those who observe it. The Torah must be read in Hebrew. For those who do not understand Rashi or Onkelos, it is acceptable to use a translation incorporating Chazal's teachings, not a literal translation.