Likutei Moharan 1:3/ליקוטי מוהר"ן א׳:ג׳

13. It is through this that all the prayers and petitions are accepted. For the main reason the requests are not accepted is that the words lack grace and do not penetrate the heart of the one being asked. It is as if there were no place in his heart for the words to enter, because the petitioner is lacking the grace needed for the words to enter the heart of the one he petitions.

2But, by means of the Torah—through which the Nun and the Chet are joined and bound together— CheiN (grace) is produced. This is why the Torah is called “yaalat CheiN.” The person then merits that his words are words of charm, and so his words and requests are received. As is the case when someone speaks with chein, the matter penetrates the heart of the one petitioned—i.e., the one being asked.

3This is the concept of the tav. That is, by the Chet and Nun being joined and bound, producing CheiN, the TaV is made. This suggests etching and marking, as in (Ezekiel 9:4), “and hiTVita TaV (inscribe a mark).” By means of the chein, a space is carved out and marked in the heart of the one who is petitioned to accept the request. For as a result of the grace, his words are accepted.

4Thus it is that the chein etches a place in the heart of the one who is being petitioned, so that the other’s words may enter his heart and cause the request to be accepted. This etching and marking is the concept of the tav. This is the meaning of (Ecclesiastes 9:17), “The words of the wise are heard [for they are spoken] b’nachat (gently).” Specifically nachat —i.e., the aspect of CheiN and the Tav, which together spell NaChaT. Then, his words are heard and his request is accepted.