On WhatsApp for Android you can easily block a contact, so you won't receive any message from that blocked person. To unblock / block a contact on WhatsApp for Android, do as follows:
1. Open WhatsApp on your Android device
2. Tap the 3dot icon on the top right and then touch the Settings.
3. Tap the Account option and go to the Privacy settings
4. Under the Messaging settings, tap to open the Block Contacts option
5. Now, tap the Add icon on the top right and start selecting the contacts to block
6. To unblock a contact on WhatsApp for Android, open the list of blocked contacts, tap the one to unblock and touch the Unblock option