Red Bud Showing Wilt
Redbud trees can suffer quite a bit from stress in the transplant process, so it is likely this wilting is a sign of stress on the tree. Newly planted trees, and redbuds in particular, need regular slow, soaking watering after transplant to reduce the stress of planting. It is possible the wilt is simply an indication of drought stress, but a stressed redbud tree does become more susceptible to Botryosphaeria canker, which can result in wilting of the leaves. Click here for a previous question and answer with more information on Botryosphaeria canker in redbud trees. If the tree does have Botryosphaeria canker, follow the directions on how to prune out infected parts as mentioned in the link above.
In either case, it will be important to reduce stress on the tree through regular watering. You should plan on applying about 15-20 gallons of water each time the tree is water, applied slowly over a number of hours. This can be done using a "tree gator" bag which can be filled up with 20 gallons of water which will slowly seep out into the soil. You can also provide a similar slow release of water using a 5 gallon bucket with a few small holes drilled in the bottom. Perhaps the easiest method is to place a garden hose at the base of the tree and turn the water on to a slow trickle for a few hours, being sure to move the hose around to different sides of the tree a few times while watering. Watering once a week now through the fall should help this tree. During hot and dry weather, or if the tree is in a full sun location, you may want to up the watering to two or three times a week. However, be careful that the soil does not become too soggy, as overly wet conditions can cause stress on the tree as well.
If the tree has not been mulched, adding a layer of wood chip or other organic mulch will help maintain moist soil conditions. Mulch should be applied about three inches thick around the bottom of the tree, extending to the edge of the tree canopy or beyond. The mulch should taper off in thickness as you get near the trunk and no mulch should be in contact with the tree trunk.