(Ibid. 15) "By word of two witnesses, or by word of three witnesses, shall a thing be established": not through their script or through their interpreter. "shall a thing be established": From here it was stated: R. Eliezer says: He forewarns her (a suspected wife) in the presence of two witnesses (not to secrete herself with the suspect), and causes her to drink (the bitter waters of the sotah) by the word of one witness (that she secreted herself).
R. Yehoshua says: He forewarns her in the presence of two and causes her to drink by the word of two. For it would follow: If the latter testimony (that she had secreted herself), which forbids her universally (i.e., even to her husband), were by one witness, how much more so would the former testimony (to her forewarning), which does not forbid her universally (i.e., she is permitted to her husband) — how much more so should it be acceptable with one witness. It is, therefore, written (Devarim 24:1) "for he has found in her a thing of nakedness." And it is written here "By word of two witnesses … will a thing be established" — Just as here, two (are required), so, there, two. How much more so (are two required for) the latter testimony (that she had secreted herself.) For if the first testimony, which does not forbid her universally (i.e., to her husband) is not valid with fewer than two, then the latter testimony, which does forbid her to her husband, how much more so is it invalid with fewer than two. This is the intent of (Bamidbar 5:13) "and there be no witness in her" (see there).