Negative commandment · Lo Ta’aseh #64 of 613
Not to test the promises of G-d
שלא לנסות את דבר ה'
The verse · Devarim 6:16
לֹא תְנַסּוּ אֶת־ה׳ אֱלֹהֵיכֶם כַּאֲשֶׁר נִסִּיתֶם בַּמַּסָּה
“Do not tempt the Lord your God, as you tempted him in Massa.”
The Rambam’s words
Not to test the promises of G-d, as [Deuteronomy 6:16] states: "Do not test G-d, your Lord."
שלא לנסות את דבר ה', שנאמר "לֹא תְנַסּוּ אֶת ה' אֱלֹהֵיכֶם" (דברים ו, טז).
Why · Sefer HaChinuch #424
To not test a true prophet more than is necessary
“It is from the roots of the commandment [that it is] since harm will be [caused] with superfluous testing of true prophets, as sometimes people that are jealous of him and hurt from his status will disagree with him from this.”
Who & when
“And this commandment is practiced by males and females in every place and at all times when a prophet arises for Israel.”
Where in the Mishneh Torah
Hilchot Foundations of the Torah הלכות יסודי התורה