אִם־שַׁנּוֹתִי֙ בְּרַ֣ק חַרְבִּ֔י וְתֹאחֵ֥ז בְּמִשְׁפָּ֖ט יָדִ֑י אָשִׁ֤יב נָקָם֙ לְצָרָ֔י וְלִמְשַׂנְאַ֖י אֲשַׁלֵּֽם׃
Wenn ich mein glitzerndes Schwert schleudere und meine Hand das Gericht ergreife; Ich werde mich an meinen Gegnern rächen und diejenigen belohnen, die mich hassen.
Rashi on Deuteronomy
אם שנותי ברק חרבי means, IF I SHALL WHET THE BLADE OF MY SWORD, so that it shall have a flash (ברק); splendeur in old French
Sforno on Deuteronomy
אם שנותי, even though I had sharpened the blade of My sword against the Jewish people during the time of their exile, את ברק חרבי, this was only the flashing appearance, not the פי החרב, the lethal part of the sword.
Rashbam on Deuteronomy
אם שנותי, from the root שנן, to sharpen. The same root is used in connection with sharpening a sword in Psalms 64,4 אשר שננו כחרב לשונם, “who have sharpened their tongue as if it were a sword.” The double consonant in the root שנן is similar to such roots as סבב and בלל. Just as these roots sometimes drop the last consonant, compare Samuel I 22,22 סבותי בכל נפש בית אביך or in Psalms 92,11 בלותי בשמן רענן, so in our verse instead of שננתי the Torah writes שנותי.