Shir ha'Shirim Rabah 1:4: When Yisrael wanted to receive Oz (the Torah), Hashem requested guarantors. He did not accept the Avos (for also they transgressed), and not the Nevi'im. Yisrael said that their children will be Arevim; Hashem accepted.

Rashi (2): You put Your Shechinah in the Mikdash, and enacted that Leviyim and Kohanim thank (sing to and serve) You - they are humans, who grow up in filth. "Olelim" is [an expression of disgrace,] like "v'Olalti ve'Afar Karni" (Iyov 16:15); infants are called so, due to filth. "Yonkim" are [nursing] babies (Yonkei Shadayim).

Radak: Nursing is the first wonder in a man who comes to the world. One must thank the Creator and recognize his power based on His deeds seen in Shamayim va'Aretz, and man's body. A putrid drop [of semen] becomes blood, and grows slowly into limbs. Tehilim 139 discusses this. Just like the Yesod (foundation) is the start of a building, nursing is the start of recognizing Hashem's Chesed on man. The nipple is just the right size. The milk comes from [over the heart,] the place of understanding (Brachos 10a), unlike in animals. This shows that a conductor planned all this, unlike Iyov, who said that all is nature and chance.

Radak citing Ibn Ezra: From the time that a child can speak, he receives the power of his Neshamah to recognize its Creator.

Radak citing R. Moshe Jiktila: Infants, who cannot speak, they demonstrate Your great Chesed. You 'finance' them and make their bodies grow in height and width.

Malbim: Olelim v'Yonkim refers to man, whose physical body is very weak. From birth he is much weaker than baby animals. Their latent power of speech and intellect is the ultimate Chachmah and wonder in Hashem's creation. Man founds Oz; he completes the creation. Everything outside the earth, e.g. celestial bodies, are pillars, branches and embellishments to this foundation.

Rashi: To inform them that we are Your nation (some texts - servants).

Radak: Refer to 8:3:3:2.

Radak citing Ibn Ezra: It is to refute deniers of Hashem. Malbim - they are called Oyvim, Sone'im and Tzorerecha.

Rashi: It ceases the shame from them. They say 'you are no better than other nations.'

Radak: This is due to (to refute) deniers ¹ , who say that everything is nature and chance. Even though this Chesed (nursing) is also in animals, man was given understanding and intellect to recognize Hashem's deeds and thank Him for everything. All was created for man's benefit!

Malbim: If deniers of Hashem do not recognize Him from the creation in general, they must admit that there is a Creator when they look at and investigate the wonders that come together in man's formation.