God disdains the forced services of men, and chooses to be worshipped freely and willingly
I'm sure the Calvinist has some theological explanation for Calvin's apparently clear statement here. He is stating that God Himself will never "force" men against their wills to serve Him. For such an idea is abhorrent to God. I think it is reasonable to conclude that Calvin is arguing that our service to God must originate from our own free will. We must choose to serve him.
Behold, the days come, saith the Lord, that I will make a new covenant with the house of Israel, and with the house of Judah (1599 Geneva Bible)
That God will renew his covenant with them, so that all these blessings they shall have, not by providence only, but by promise, and thereby they shall be both sweetened and secured. But this covenant refers to gospel times, the latter days that shall come; for of gospel grace the apostle understands it (Hebrews 8:8; Hebrews 8:9, c.), where this whole passage is quoted as a summary of the covenant of grace made with believers in Jesus Christ. Observe, 1. Who the persons are with whom this covenant is made--with the house of Israel and Judah, with the gospel church, the Israel of God on which peace shall be (Galatians 6:16), with the spiritual seed of believing Abraham and praying Jacob. Judah and Israel had been two separate kingdoms, but were united after their return, in the joint favours God bestowed upon them so Jews and Gentiles were in the gospel church and covenant.
-Henry's Complete Commentary on the Bible (Jeremiah 31, excerpt)
Note the use of "they" and them" in his opening statement. We like to note the importance of pronouns. Henry is pointing to "the house of Israel, and the house of Judah," yet he is so determined to see God as having only one plan for all men of all ages that he forces himself to make Israel and Judah into the "church" (as he defines it). He states "but this covenant refers to gospel times" without warrant. He refences Paul's quote of the passage in Jeremiah, but fails to note that Paul, in the Acts Age, still speaks of the New Covenant as yet future and having not come in yet. The apostle also continues to use "the house of Israel, and the house of Judah."
“Behold, the days are coming, says the Lord, when I will make a new covenant with the house of Israel and with the house of Judah— not according to the covenant that I made with their fathers in the day when I took them by the hand to lead them out of the land of Egypt; because they did not continue in My covenant, and I disregarded them, says the Lord. For this is the covenant that I will make with the house of Israel after those days, says the Lord: I will put My laws in their mind and write them on their hearts; and I will be their God, and they shall be My people.
-Hebrews 8:8-10 (NKJV)
In that He says, “A new covenant,” He has made the first obsolete. Now what is becoming obsolete and growing old is ready to vanish away.
-Hebrews 8:13 (NKJV)
The word translated "becoming obsolete" is the Greek word "palaióō." The King James Version translates this word as "decayeth." The idea is that it is essentially dead, but it has not fully gone away. The New Covenant could not come in because Israel had not repented.