Bráchá levátálá

This baraita is apparently self-contradictory. On the one hand, you said that one who recites havdala in the Amida prayer is more praiseworthy than one who recites havdala over the cup of wine, indicating that reciting havdala in the Amida prayer alone is sufficient. And then it is taught: If one recited havdala in this, the Amida prayer, and that, over the cup of wine, may blessings rest upon his head. And since he fulfilled his obligation to recite havdala with one, he is exempt, and the additional recitation of havdala over the cup of wine is an unnecessary blessing. And Rav, and some say Reish Lakish, and still others say Rabbi Yoḥanan and Reish Lakish both said: Anyone who recites an unnecessary blessing violates the biblical prohibition: “Do not take the name of the Lord your God in vain” (Exodus 20:7).

...One who is standing by an aqueduct, one blesses upon the water annd drinks the water, even though the water that one is drinking was not in front of the person when the person blessed upon it, since the person had intended to drink from the flowing water from the outset....

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However in a case where one took a cup of beer in his hand and thought it was wine, and began reciting the blessing thinking it was wine, meaning he intended to recite: Who creates the fruit of the vine, and upon realizing that it was beer he concluded the blessing with that which is recited over beer: By Whose word all things came to be, what is the halakha?

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The Gemara responds: You cannot say that Deuteronomy 28:59 is referring to one who pronounces the name of Heaven in vain, as it is written: “You shall not curse the deaf” (Leviticus 19:14), which prohibits all curses, even those using God’s name. Granted, if you say that Deuteronomy 28:59 is referring to cursing another, one can say that the separate warning of punishment for this prohibition is from here, as it is written: “You shall not curse the deaf.” One verse articulates the prohibition, and the other indicates liability for punishment. But if you say that Deuteronomy 28:59 is referring to pronouncing the name of Heaven in vain, from where is the warning of this prohibition? A prohibition requires two verses to include liability for punishment.

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This baraita is apparently self-contradictory. On the one hand, you said that one who recites havdala in the Amida prayer is more praiseworthy than one who recites havdala over the cup of wine, indicating that reciting havdala in the Amida prayer alone is sufficient. And then it is taught: If one recited havdala in this, the Amida prayer, and that, over the cup of wine, may blessings rest upon his head. And since he fulfilled his obligation to recite havdala with one, he is exempt, and the additional recitation of havdala over the cup of wine is an unnecessary blessing. And Rav, and some say Reish Lakish, and still others say Rabbi Yoḥanan and Reish Lakish both said: Anyone who recites an unnecessary blessing violates the biblical prohibition: “Do not take the name of the Lord your God in vain” (Exodus 20:7).

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