And Hashem said to Moshe, "Come to Paroh" (Shmos 10:1).

The posuk doesn't say "Go to Paroh". Rather, it says "Come". One cannot go from before Hashem Yisborach. His Glory fills the world (Yeshaya 6:3). It is more appropriate to use the term "come" which means "Come with Me for I am with you".

--In the name of the Kotzker Rebbe

For I have hardened his heart (Shmos 10:1).

Since the Makkos were performed in order to soften Paroh's heart and turn him towards good, his free choice was no longer balanced between good and evil. Therefore, Hashem hardened Paroh's heart to protect his free choice and keep it balanced.

It is for this reason that the Medrash explains the word Hichbaditi, 'I hardened', as a derivative of the word Kavaid, a liver. Hashem is saying that he made Paroh's heart like a liver. The nature of the liver is to not absorb anything while it is being cooked. Additionally, the more a liver is cooked the harder it becomes.

--HaDrash V'HaIyun

And also our livestock will go with us...from it we will take to serve Hashem, our Al-Mighty (Shmos 10:26).

Our animals will go with us willingly because they desire to ascend as a Korban before Hashem. This is similar to what our Sages say about the cow that Eliyahi Hanavi brought as a Korban. It ran towards the altar in joy, while the cow that the false prophets were offering refused to go towards their altar. We can learn a lesson from this on how to serve Hashem. If an animal, that has no understanding, desires to become a Korban to The Al-Mighty, all the more so should people, who have an understanding of Hashem's greatness, be filled with desire to serve Him. From it we will take... The Hebrew word for 'lesson' (lekach) has a common root with the Hebrew word for 'take' (nikach). [We take a lesson from the animals].

--The Malbim

And Hashem said to Moshe and Aharon in the land of Egypt, saying 'This month is for you' (Shmos 12:1).

On the 25th of Elul during Creation, Hashem created the planets and stars. Sanctification of the new month and the power to intercalate the calendar was in the hands of HaKodosh, Boruch Hu. He passed the knowledge of this process on to Odom who gave it to Chanoch. Chanoch gave it to Shaim, Shaim to Avrohom Avinu, Avrohom to Yitzchok, and Yitzchok to Yaakov. Now in Egypt, Hashem said, 'Tell B'nei Yisroel that the secret of the calendar and sanctification of the month is in your hands'.

--Pirkei D' Rebbi Eliezer 8

And the darkness will be tangible (Shmos 10:21).

Regarding the plague of darkness and the tangibility of it, one should not understand it as the darkening of the sun in the sky. The sun remained as bright as always throughout the Makkah. Rather, the paths through which the light travels were blocked for the Egyptians and Hashem stopped the light from entering these paths. After doing this, Hashem made the darkness heavy to the point of being tangible and someone sitting could no longer get up and someone standing could no longer sit down. The Jews continued to see light throughout this plague because Hashem didn't close off the paths for the light in their dwellings. That is why there was darkness for the Egyptians and light for B'nei Yisroel.

--Rabbeinu Bechaye

Behold, I will bring a plague of locust into your border (Shmos 10:4).

How did Moshe know about this plague? Hashem never told him He would be bringing locusts.

Moshe saw the abbreviations for the Makkos carved into the staff and figured out that the Aleph of B'A'CHa'V alluded to Arbeh, locusts.

--Daas Zekeinim M' Baalei Tosfos

And Hashem will skip over the entrance (Shmos 12:23).

Generally, Heaven doesn't save a person from trouble unless the person first makes an effort on his own to repent. Our Sages say, Hashem says, 'Open for me an entrance the size of the eye of a needle and I will open for you an entrance the size of a great hall'. An entrance, even extremely small, must be opened first by the person. However, B'nei Yisroel were engulfed in the impurities of exile in Egypt and had no merits of their own with which to open any entrance. Nevertheless, Hashem had mercy on them and opened up the entrance to redemption for them without considering that they had not even opened an entrance the size of the eye of a needle on their own.

Hashem will skip over the entrance. Hashem skipped over the usual requirement that a person has to open the entrance first. He opened the entrance to redemption for them.

--Botzina D'Nihora from R' Boruch of Medzhibozh