What should Hashem guard?
'Rashi': Consider this donation to be a great donation and Tzedakah.
Radak (17): Guard this for them forever, that their intents and hearts be proper with you.
Malbim: Guard the merit of their donation and the straightness of their hearts.
Why did he say "l'Yetzer Machshevos Levav Amecha"?
'Rashi': The Yetzer of the two parts of their hearts and their intents are for the good. This refers back to "You examine Levav" (verse 17).
Malbim: Their merit should help that ideas that come on their hearts should always be good, of Tzedakah and Yir'as Hashem.
What is the meaning of "v'Hachen Levavam Elecha"?
'Rashi': Make the two parts of their hearts Shalem, to be one heart to You.
Malbim: Even if a bad idea comes on their spirit, the heart should overpower to subdue the bad idea, and Yir'as Hashem will rule.
