The Ben Ish Hai (Rav Yosef Haim of Baghdad, 1833-1909), in Parashat Balak, discusses the case of a non-Jew who deliberately touches a Jew’s wine for the purpose of rendering it forbidden. For example, if a non-Jew becomes angry at a Jew, and in his fury he shakes the Jew’s bottle of wine so that it would become forbidden for the Jew, does the bottle of wine in fact become forbidden?
The Ben Ish Hai cites different views on this issue. He notes that whereas the Rambam (Rabbi Moshe Maimonides, Spain-Egypt, 1135-1204) ruled that the wine becomes forbidden in such a case, others ruled that the wine is permissible, because the Sages did not forbid wine touched by a non-Jew under these circumstances. As for the final Halacha, the Ben Ish Hai writes that in situations of "Hefsed Meruba" – where a substantial financial loss is at stake, such as when dealing with expensive wine or a large quantity of wine – then the wine is certainly permissible and may be used for drinking or any other form of benefit. If, however, the financial loss at stake is not so substantial, then it is preferable not to use the wine. Even in such a case, the Ben Ish Hai emphasizes, the wine is permissible according to the strict Halacha and one may rely on the lenient position. He notes that this applies even if we do not know with absolute certainty that the gentile specifically intended to render the wine forbidden, but we can reasonably assume that this was his intent in light of the circumstances surrounding the incident.
In the next passage, the Ben Ish Hai cites a particularly stringent ruling of Rabbi Menahem Hababli forbidding wine that a non-Jew looked upon, but did not touch. According to this view, one must ensure to keep his wine hidden or covered so that no non-Jew can look at it.
Although there are people who follow this custom, according to the strict Halacha wine that a non-Jew looked at is permissible. Refraining from such wine constitutes a "Midat Hasidut" – a measure of special piety – and not an actual Halachic requirement. The Ben Ish Hai notes that Moslems, who worship the single Creator, are not considered idolaters, and there is thus no concern whatsoever in using wine that a Moslem has looked at, not even on the level of "Midat Hasidut."
Although Halacha does not follow the view of Rabbi Menahem Hababli, his ruling demonstrates the severity of this prohibition against non-Jewish wine. If some authorities go so far as to forbid wine that was looked at by a non-Jew, then even if we do not accept this position, it emphasizes just how careful we must be when it comes to non-Jewish wine.
Summary: If a gentile touched kosher wine with the specific intent to make it forbidden, the wine is permissible, as long as we can reasonably assume that this was his intent. Preferably, however, one should not use the wine, unless a substantial financial loss is at stake. Some people have the practice as a measure of special piety to ensure that a gentile does not even look at their wine, as there is one opinion that forbids wine that a non-Jew looked upon. This practice is not required according to the strict Halacha, but it demonstrates the severity of the prohibition against non-Jewish wine.
