Is this a wild rabbit or a domestic, what color is it? All white and mixed with white rabbits are domestic, as are variations of greys, tans, spotted, black, black & white etc. Some domestic breeds have the wild Agouti coloring as well and any lop eared rabbit is also a domestic variety. If it is a domestic it would be best to try and catch it. Domestics need a commercial alfalfa pelleted feed and also grass or oat hay and water, of course.
No celery, ever, celery is bad for rabbits, binds them up, no iceberg lettuce, some dark green leaf lettuces are okay in small amounts, the occasional apple slices, carrots, or anything like wild blackberry leaves, apple leaves, dandelion greens, are fine for the occasional treats. Dry oats are also good if bunnies have runny bunny poo. haha
It all depends if it is a domestic escape or a wild rabbit or hare. If it is a domestic I would put out hay, alfalfa, timothy or oat hay or buy some commercial pelleted feed.
Remember Peter rabbit, he got a baaad tummy ache from eating all the goodies in Mr. Macgregors garden. You can read up more online but this is some basic info. Also, be careful, bunnies can bite, hard, if this bunny is not very tame watch your fingers if you are trying to lure it in as a potential pet. If it is, indeed, an escaped domestic you could easily tame it down and keep it as a pet.