Rashi #1: How could I not sin - my formation was via Bi'ah; many sins come from it ¹ .

Rashi #2: My primary formation was from male and female; all are full of sin.

Radak citing Ibn Ezra: Due to lust planted in man's heart, it is as if he was conceived in sin. At the time of birth, the Yetzer ha'Ra is planted in the heart.

Radak: Some say that this is a hint to Chavah; she gave birth only after she sinned.

Radak citing his father: David comes to minimize his sin. Man is created from a drop of semen, via Bi'ah. One who sows bitter seeds, the tree and fruit will be bitter, according to nature. All matters follow what gave birth to them. It is not a great matter if his Yetzer ha'Ra overpowers him and he sins in this. It is a great matter if he overpowers his Yetzer for this! Theft, murder and all other sins are not from his nature; it is a great matter if he sins in them.

Malbim: Man's nature is prepared for sin, i.e. crookedness of intellect. His intellect is incarcerated in physicality, so it easily errs in matters of investigation.

Radak (from Vayikra Rabah 14:5): Even the biggest Chasid, it is impossible that he will not have some sin. David said, did my father intend to father me? He intended only for his own needs! We see that after they do their needs, they face away from each other, and You enter every drop from him [to form me] - "Ki Avi v'Imi Azavuni va'Shem Ya'asfeni" (27:10).

Rashi: It is an expression of Bi'ah, like "va'Yechamnah ha'Tzon b'Vo'an Lishtos" (Bereishis 30:38).

Radak: She is heated. From the heat comes the drop of semen from which the child is formed.

Malbim: Conception is via heat due to lust for Bi'ah; the child remains with a nature of lust, so he is prone to sin via it.

Radak: She causes a male to be born more than the father does. "Ishah Ki Sazri'a v'Yaldah Zachar" (Vayikra 12:2) - if she is Mazri'a (sends her seed) first, she will give birth to a male (Brachos 60a).