John Gill Commentary 1 Chronicles 29:17

"I know also, my God, that thou triest the heart, and hast pleasure in uprightness. As for me, in the uprightness of my heart I have willingly offered all these things: and now have I seen with joy thy people, that are present here, offer willingly unto thee." — 1 Chronicles 29:17 (ASV)

I know also, my God, that you test the heart Searches it, and knows it perfectly, whether what is done is from it:

and have pleasure in uprightness ; in what is done in sincerity and uprightness of heart:

as for me, in the uprightness of my heart I have willingly offered all these things ; for the truth of which he could appeal to the heart searching God:

and now have I seen with joy your people, which are present here, to offer willingly to you ; he judged by what they did, and their manner of doing it, that it was done in the uprightness of their hearts also, as his were, which gave him sensible joy and pleasure.