O que significa and he absorbed the oblation as a desert drinks the rain that can coax from it no promise of blossom or fruit ?

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It means that he accepted the oblation (something which is offered to God)
as a desert drinks the rain (as sand absorbs the water gladly, as if it were thirsty, signifying that the was as glad to accept it)
that can coax (persuade) from it
This part means that the person upon having that oblation felt so good that he could be a desert which has given up on its natural way and has started to bear fruit. As if the desert has given up the promise to bear no fruit.
Which is kind of a miracle.
This extract is talking about how greatful and happy the person feels.