Targum for Exodus 4:8

וְהָיָה֙ אִם־לֹ֣א יַאֲמִ֣ינוּ לָ֔ךְ וְלֹ֣א יִשְׁמְע֔וּ לְקֹ֖ל הָאֹ֣ת הָרִאשׁ֑וֹן וְהֶֽאֱמִ֔ינוּ לְקֹ֖ל הָאֹ֥ת הָאַחֲרֽוֹן׃

And it shall come to pass, if they will not believe thee, neither hearken to the voice of the first sign, that they will believe the voice of the latter sign.

Targum Jonathan on Exodus