לאמר means that when one davens, one should express himself clearly. He shouldn't speak in vague, ambiguous terms, leaving room for doubt in the meaning of his words.
We shouldn't say, "Hashem knows what I mean." Instead, speak clearly and say precisely what you want to say.
Reb Moshe Midner zt'l asked: Why is expressing oneself coherently and clearly in tefillah so important? Hashem knows what we need, even if we don't express ourselves!
Reb Moshe Midner answers that one must know that he is speaking with Hashem. If he has this emunah, he will express himself very well. He will speak to Hashem like a child speaking with his father. The problem with not being articulate with the tefillah is that it shows that he doesn't really recognize that he is speaking to Hashem.
Reb Moshe Midner zt'l taught this lesson to his friend, Reb Hershel Mikrinki hy'd. Reb Moshe Midner concluded, "Whenever you need salvation, say two chapters of Tehillim and then express your needs before Hashem yisbarach in your own words. Express yourself well. Don't hint, don't be ambiguous, don't be stingy with your words. And then Hashem will answer your tefillos. And I request that when you do this, mention my name, too: Moshe ben Rachel, so I too will benefit from this" (Sod Siach Chassidim).
It states in this week's parashah (4:7), גוי מי כי אליו קראנו בכל אלקינו 'כה אליו קרובים אלקים לו אשר גדול, "Which great nation has a god close to them as Hashem our G-d is close to us whenever we call out to Him."
The Yerushalmi explains that to the human eye, it appears that avodah zarah is close to its worshippers because the avodah zarah and their owners reside in the same home. They are very close. It also seems to us that Hashem is very far away because we don't see Him. But the opposite is true. As the Yerushalmi writes:
"No one is closer [than Hashem and the Jewish nation]. Hashem seems to be far away because the distance from the earth to heaven is [vast]... Yet, when a Yid comes to the beis hakneses and stands behind the amud and davens silently, Hakadosh Baruch Hu listens to his tefillos. Is there anything closer? Hashem listens to him as though he is whispering into Hashem's ear."
When we have this emunah, we will express ourselves well.
