15 Still, however, the woman has her mind on the flesh: she is delighted with the thought of thirsting no more, and fancies that this was promised to her by the Lord after a carnal sense; which it will be indeed, but in the resurrection of the dead. She desired this now. God had indeed granted once to His servant Elias, that during forty days he neither hungered nor thirsted. Could not He give this always, seeing He had power to give it during forty days? She, however, sighed for it, desiring to have no want, no toil. To be always coming to that fountain, to be burdened with a weight with which to supply her want, and, when that which she had drawn is spent, to be obliged to return again: this was a daily toil to her; because that want of hers was to be relieved, not extinguished. Such a gift as Jesus promised delighted her; she asks Him to give her living water.
Source: Tractates on the Gospel of John (New Advent)