惠崇 is the painter, not the poet: a Northern Song monk known for small scenes of geese, ducks and river banks.
苏轼 wrote two quatrains on his painting in 1085, and the first is the famous one:
竹外桃花三两枝,
春江水暖鸭先知。
蒌蒿满地芦芽短,
正是河豚欲上时。 'Beyond the bamboo, two or three sprays of peach blossom; when the spring river warms, the ducks know first. Wormwood covers the ground and the reed shoots are short: just the time when the puffer fish swim upriver.'