1 Samuel 20:26

But Saul said nothing that day, for his thought was, Something has taken place making him unclean; it is clear that he is not clean.

Leviticus 15:5

And anyone touching his bed is to have his clothing washed and his body bathed in water and be unclean till evening.

Leviticus 11:24

By these you will be made unclean; anyone touching their dead bodies will be unclean till evening:

Leviticus 11:27

Any four-footed beast which goes on the ball of its foot, is unclean to you: anyone touching the dead body of one of these will be unclean till evening.

Leviticus 7:20-21

But he who is unclean when he takes as food the flesh of the peace-offerings, which are the Lord's, will be cut off from his people.

Leviticus 11:31

All these are unclean to you: anyone touching them when they are dead will be unclean till evening.

Leviticus 11:40

And he who makes use of any part of its body for food is to have his clothing washed and be unclean till evening; and anyone taking away its body is to have his clothing washed and be unclean till evening.

Leviticus 15:16-17

And if a man's seed goes out from him, then all his body will have to be bathed in water and he will be unclean till evening.

Leviticus 15:19-21

And if a woman has a flow of blood from her body, she will have to be kept separate for seven days, and anyone touching her will be unclean till evening.

Numbers 19:16

And anyone touching one who has been put to death with the sword in the open country, or the body of one who has come to his end by a natural death, or a man's bone, or the resting-place of a dead body, will be unclean for seven days.

1 Samuel 16:5

And he said, In peace: I have come to make an offering to the Lord: make yourselves clean and come with me to make the offering. And he made Jesse and his sons clean, and sent for them to be present at the offering.

Treasury of Scripture Knowledge

Summary

Nevertheless Saul spake not any thing that day: for he thought, Something hath befallen him, he is not clean; surely he is not clean.

Bible References

He is not clean

Leviticus 7:21
And anyone who, after touching any unclean thing of man or an unclean beast or any unclean and disgusting thing, takes as food the flesh of the peace-offerings, which are the Lord's, will be cut off from his people.
Leviticus 11:24
By these you will be made unclean; anyone touching their dead bodies will be unclean till evening:
Leviticus 15:5
And anyone touching his bed is to have his clothing washed and his body bathed in water and be unclean till evening.
Numbers 19:16
And anyone touching one who has been put to death with the sword in the open country, or the body of one who has come to his end by a natural death, or a man's bone, or the resting-place of a dead body, will be unclean for seven days.

Basic English, produced by Mr C. K. Ogden of the Orthological Institute - public domain