1)
Which people did he fatigue?
1.
Rashi citing Targum Yonasan: Hashem's Nevi'im.
2.
Malbim: You attribute fatigue and lack of strength to the Nevi'im, and do not believe that the Navi has power to do a sign or wonder.
2)
How does he fatigue Hashem?
1.
Rashi: He knows that you do not believe in Him, and you fatigued Him with your evil.
2.
Radak citing Targum Yonasan: Sehalun even the words of Hashem. You do not believe in them, and think in your hearts that He is [too] weary and weak to fulfill His words. Hal'os and Yegi'ah are with words or actions.
3.
Malbim: You attribute fatigue and lack of strength also to Hashem, and do not believe in His signs.