Maran (author of the Shulchan Aruch), in the Orach Chayim section, Siman 116, discusses the Beracha of "Refa’enu," the eighth Beracha of the Amidah. He observes that we recite this Beracha in the plural form: "Refa’enu Hashem Ve’nerafe" literally translated means, "Heal us, G-d, and we will be healed." Yet, the verse in Yirmiyahu (17:14) upon which this prayer is based, is written in the singular form; "Refa’eni Hashem Ve’erafe", translated as "Heal me, G-d, and I will be healed." So Maran writes that Halacha generally forbids changing the way verses are written from singular to plural form, but this restriction only applies when is reading the original text itself. For example, if a person opens the Book of Yirmiyahu and begins reading, he may not change the verse from singular to plural form. But when a person incorporates a Pasuk as part of his prayer, he may change it from singular to plural. Therefore, in the Amidah, when we pray and petition G-d, we may change the language of the verse from the singular to the plural form, so that we pray on behalf of the entire Jewish people.

This Halacha in the Shulchan Aruch resolves a question that has been raised concerning the practice we have at weddings for the Rabbis under the Chupa (canopy.) There they extend a blessing to the new bride and groom based on a Pasuk in the Book of Rut. The Rabbis traditionally bless the couple with the blessing given to Boaz when he married Rut (Rut 4:11) which reads; "May G-d make the woman coming into your home like Rachel and like Leah, both of whom built the House of Israel, and may you be successful." Now, the final phrase of this blessing; "Va’aseh Chayil" ("May you be successful"), is written in the singular form, as it was said only to Boaz. Under the Chupa however, the Rabbi extends this blessing to both the Chatan (groom) and Kalla (bride), and he therefore changes it to the plural form and says "Va’asu Chayil." The question has been asked how is it that Rabbis are able to alter the syntax of the verse. So based on the aforementioned Halacha in the Shulchan Aruch, the answer is abundantly clear. The Rabbis are not reading Megilat Rut under the Chupa. They are instead reciting a prayer on behalf of the new couple, and are therefore allowed to change the Pasuk to the plural form.

This discussion brings us to the famous principle of "Al Titosh Torat Imecha", literally meaning, "Do not abandon the teaching of your mother," which admonishes against forsaking the customs that have come to us through tradition. Even when a custom initially appears incongruous with Halacha, we must remember that our traditions are, as the Hachamim often comment, rooted "Be’harere Kodesh" – "in the holiest mountains." Therefore, if at first a custom seems to us incorrect, we must thoroughly investigate the matter before rashly rejecting the custom.

In conclusion, Halacha forbids changing the formulation of a Pasuk from singular to plural form while reading the Biblical text, but if one incorporates a Pasuk into his prayers, he may change its syntax to the plural form.