Rashi: He will pay up from the nations.

Radak: He will come b'Chozek Yad. He will not need another hand. We find like this, that Yad is masculine - "v'Hine Vo Megilas Sefer" (Yechezkel 2:9).

Malbim: This is why you need not fear. One does not fulfill his word due to lack of ability, or lack of desire. The former does not apply - He will come with strength! Also refer to 40:10:2:2, 40:10:3:3, 40:10:4:3.

Radak: It will stand for Him to rule over nations.

Malbim: A king who promises to help a nation, he cannot fulfill if his generals and troops will not agree with him. Hashem's rule does not depend on others.

Rashi: It is prepared with Him for the Tzadikim.

Radak: It is what He will give to those who trust in Him in Galus.

Malbim: One who promises to save, if he hoped to be paid, and now he does not need the reward, or the opponent offers more reward, or if the one whom he promised to save will not be able to pay the reward, his desire can change, and he will not fulfill his promise. Hashem does not get reward from anyone!

Rashi: The wages that it is upon Him to pay them.

Radak: It is the wages of those who work honestly. Grammatically, it can be attributed to Him or them (the workers). The same applies to "b'Veis Tefilasi", "Shamati Es Tefilasecha" (56:7, 38:5). The word Sechar is omitted. This is like "Lo Salin Pe'ulas Sachir" (Vayikra 19:13); it means Sechar Pe'ulas Sachir.

Malbim: When Hashem promised, it is as if He already did. His desire will not change.