Thou hast proved mine heart; thou hast visited me in the night; thou hast tried me, and shalt find nothing; I am purposed that my mouth shall not transgress.
Thou hast proved ... tried me - as pure gold tested by the searching fire, and found to have no dross. The Hebrew for tried is literally 'melted me.' The preterite tenses express the past reaching on to the present: Thou hast proved me, and the result is thou findest nothing (against me in respect to insincerity), and shalt find nothing.
In the night - the time when especially good and evil thoughts in the soul are accustomed to start up, there being nothing outward to draw off the attention: 'when secrecy and solitude prompt the hypocrite to sin, and the undisciplined imagination wanders abroad like a bird of darkness after forbidden objects' (Horne). So Psalms 16:7. This psalm was probably an evening-song: cf. Psalms 17:15, "when I awake," the time of sleep suggesting the thought of the last sleep, from which the awaking shall be at the resurrection.
I am purposed that my mouth shall not transgress. The proving of the heart by God, in the beginning of the verse, has little connection with the transgression of the mouth at the end. Moreover, `aabar (H5674) can hardly, without addition, mean to transgress. The only thing in question in the context is, are the declarations of his mouth confirmed by the heart, when proved by God? Not the mouth, but the thought or heart, was the chief object of the divine search. I therefore prefer, with Hengstenberg, to translate, 'my mouth oversteps not my thought;' i:e., my heart, as proved by thee, shows that it does not differ from the statement of my mouth, whereby I claimed to be righteous - i:e., sincere before thee. х zamotiy (H2161), 'my thought,' is the infinitive, used as a noun in the accusative, and stands before the subject, "my mouth," as it is the thought that is the principal object of search.] The question is not whether he thinks otherwise than he speaks, but whether he speaks otherwise than he thinks: therefore reject Gesenius' translation, 'thy thoughts overstep not my mouth.' Compare Psalms 17:1, "my prayer goth not out of feigned lips."