What is the ruling on one who intentionally does not perform ablution out of laziness, while water is available, and then prays, and is it permissible to declare him an apostate (takfir)?

Whoever prays without purification, knowing that he is in a state of ritual impurity, his prayer is invalid, and he commits a grave sin, and he must repeat it. However, he does not disbelieve unless he deems that permissible. As for the ignorant and the forgetful, there is no sin upon them.