Комментарий к Берешит 21:24

אנכי אשבע, I will do you the favour to swear such an oath; however, you have not done me any favours as you claim to have done.

ויאמר אברהם אנכי אשבע. Abraham said: "I will swear." Abraham implied that he could counter Avimelech's arguments but had decided instead to swear as Avimelech requested.

ויאמר אברהם אנכי אשבע, implying that Avimelech on his part has to swear also. The word אשבע is spelled with the vowel chirik under the letter א, Generally, when a verb in the first person is in the passive mode, it has the vowel segol so that the combination of aleph-chirik should not be misunderstood as if it had been spelled אי.