"At the beginning of the passage, God appears and says one word: 'Abraham.' Abraham responds to God with equal conciseness: 'Hineni' ('Here I am'). This is not a declaration of location. It is a statement of existential presence. Here I am: completely, wholly for you." (source)

"The great medieval sage Rashi comments that Hineini is an expression of readiness...Thank you for your contribution this year and for joining me in proudly declaring, 'Hineini.'" (source)