In Early Modern English, the second person singular past-tense verb form typically took the -(e)st ending—and almost always -st (without the syllabic e) when the verb took the regular -ed ending, as discussed on page 165 of Charles Barber, Early Modern English (Edinburgh: Edinburgh University Press, 1997). Here in Alma 8:15, the earliest text has “thou received”, without the expected -st ending of Early Modern English. The 1920 LDS edition added the -st ending to received, but the critical text will restore the original received. For past-tense verb forms occurring with the second person singular thou, the -(e)st ending is sometimes omitted from the earliest Book of Mormon text; see, for instance, the discussion under 2 Nephi 24:12 regarding “thou did” instead of “thou didst”.
Summary: Restore in Alma 8:15 the second person singular past-tense form received without the expected Early Modern English ending -st.