Deuteronomy 3:23

"And I pleaded..." The word 'pleading' always refers to a freewill gift. Even though the righteous can and should rely on their good deeds, one does not pray to God for anything other than a freewill gift, as God said to Moses in Exodus 33:19, "I shall give grace whomever I want."

And I sought mercy at that time from before the Lord, saying:

I begged grace i.e., I had already begged grace. Scripture has just mentioned [: 21] Moshe’s instructions to Joshua; but Moshe instructed Joshua only in consequence of “I will not cross [with you]” [4: 22]. I did indeed beg God ’s grace to cross over with you, because the greatness of God “is unsearchable” [Psalms 145: 3]; and “They are new every morning; great is Your faithfulness” [Lamentations 3: 23].

AND I BESOUGHT THE ETERNAL AT THAT TIME, SAYING. [The time referred to, is] when Moses mentioned the conquest of the lands of Sihon and Og. He said, And I commanded Joshua at that time, intimating, that “I [Moses] will not go over there, for I besought the Glorious Name [to rescind the decree forbidding me to enter the Land], but He hearkened not to me and He commanded me to charge Joshua, for he shall go over before this people.”
The purport of the expression at that time is that it alludes to the time of the decree that he mentioned, Also the Eternal was angry with me [for your sakes, saying: ‘Thou shalt not go in thither’], though [Moses’] supplication is not mentioned there on the day of that event. The correct interpretation, however, is that the expression at that time refers to the time mentioned: “when I conquered Sihon and Og and I began to war against the nations given to Israel and I allocated the land to the two tribes [Reuben and Gad].” In that case, this supplication [referred to here] was offered when it was said to Moses, Get thee up into this mountain of A barim, for it was then that he sought mercy in the matter and entreated this supplication. And when G-d did not hearken to his voice, he again prayed, Let the Eternal, the G-d of the spirits of all flesh, set a man over the congregation,, Verse 16. as is mentioned there. It is this verse, And charge Joshua [that constitutes the answer to Moses’ second request]. Now, there [in the Book of Numbers] Scripture mentioned the prayer on which he was affirmatively answered [namely, the appointment of a successor], Verses 18-21. and here he mentioned this [unsuccessful prayer] in order to inform the people that, although the Land was beloved to him, he did not merit [to enter] it because of them. All this was part of his reproof.

ואתחנן אל ה, “I pleaded with the Lord. The holy tongue knows of seven different names, each referring to a different category of prayer. They are as follows: תפלה, תחינה, נפילה, פגיעה, רנה, צעקה, זעקה. Of all the types of prayer at the disposal of Moses, why did he choose only one category, i.e. תחינה? When Moses had asked G–d to reveal more of His attributes, especially His method of dealing with sinners, in Exodus 33,13, after answering Moses in part, He had concluded with: וחנותי את אשר אחון, (verse 19 there) He made it clear to Moses that whenever and howsoever He forgives a sinner or reduces the punishment for which that sinner is in line, it is a gift a תחינה. It is not something that the recipient had a claim to. Moses wanted G'd to know that though he pleads, he is aware that even if G–d responds favourably to his plea, he will never forget that this would be an outright gift rather than something he had been entitled to. Letting him cross the Jordan would be an outright gift. (Compare Tanchuma, section three on our parshah). Another reason for Moses’ choice of the word: ואתחנן, is that the numerical value of the letters in that word וחנותי we quoted from Exodus 33,19, is the same as that of ואתחנן.