Hobbes wrote:

If a covenant be made, wherein neither of the parties perform presently, but trust one another; in the condition of mere nature, (which is a condition of war of every man against every man,) upon any reasonable suspicion, it is void: *but if there be a common power set over them both, with right and force sufficient to compel performance, it is not void*. For he that performeth first, has no assurance the other will perform after; because the bonds of words are too weak to bridle men’s ambition, avarice, anger, and other passions, without the fear of some coercive power; which in the condition of mere nature, where all men are equal, and judges of the justness of their own fears, cannot possibly be supposed. And therefore he which performeth first, does but betray himself to his enemy; contrary to the right (he can never abandon) of defending his life, and means of living.

But in a civil estate, where there is a power set up to constrain those that would otherwise violate their faith, that fear is no more reasonable; and for that cause, he which by the covenant is to perform first, is obliged so to do.

With a relocation of the asterisk-tagged passage in the first paragraph:

What if a covenant is made in which the parties do not perform now, but trust one another ·to perform at an appropriate time in the future·? •If this happens in the condition of mere nature (which is war of every man against every man), the contract is void if one of the parties has a reasonable suspicion ·that the other is not going to perform·. For the one who performs first has no assurance that the other will perform later, because the bonds of words are too weak to rein in men’s ambition, greed, anger, and other passions - unless there is something to be feared from some coercive power; and in the condition of mere nature, where all men are equal and are judges of the reasonableness of their own fears, there can’t possibly be such a power. So he who performs first merely betrays himself to his enemy, which is contrary to his right (which he can never abandon) to defend his life and his means of living.

On the other hand, •if there is a common power set over both parties to the contract, with right and force sufficient to compel performance, the contract is not made void ·by the suspicions of either party to it·. When there is a power set up to constrain those who would otherwise violate their faith, that fear - ·namely, the suspicion that the other party will not perform· - is no longer reasonable; so he who has covenanted to perform first is obliged to do so.