"Brother P, you should discipline yourself to discern the sacredness of the Sabbath of the fourth commandment and should labor to raise the standard in your family and wherever you have, by example, lowered it among God's people. You should counteract the influence you have cast in this respect, by changing your words and actions. You have frequently failed to “remember the Sabbath day, to keep it holy;” you have often forgotten, and have spoken your own words upon God's sanctified day. You have been unguarded, and have upon the Sabbath joined with the unconsecrated in conversation upon the common topics of the day, such as gains and losses, stocks, crops, and provisions. In this your example injures your influence. You should reform. 2T 703.1"
"In those days saw I in Judah some treading wine presses on the sabbath, and bringing in sheaves, and lading asses; as also wine, grapes, and figs, and all manner of burdens, which they brought into Jerusalem on the sabbath day: and I testified against them in the day wherein they sold victuals. There dwelt men of Tyre also therein, which brought fish, and all manner of ware, and sold on the sabbath unto the children of Judah, and in Jerusalem. Then I contended with the nobles of Judah, and said unto them, What evil thing is this that ye do, and profane the sabbath day? Did not your fathers thus, and did not our God bring all this evil upon us, and upon this city? yet ye bring more wrath upon Israel by profaning the sabbath."
Both passages address the issue of Sabbath-breaking and the importance of keeping the Sabbath holy. Nehemiah describes specific actions, while EGW applies the principle to conversation and mental focus.
"Those who are not fully converted to the truth frequently let their minds run freely upon worldly business, and, although they may rest from physical toil upon the Sabbath, their tongues speak out what is in their minds; hence these words concerning cattle, crops, losses, and gains. All this is Sabbath breaking. If the mind is running upon worldly matters, the tongue will reveal it, for out of the abundance of the heart the mouth speaketh. 2T 703.2"
"O generation of vipers, how can ye, being evil, speak good things? for out of the abundance of the heart the mouth speaketh."
EGW directly quotes and applies the principle from Matthew 12:34 about the connection between the heart and the words spoken.