Heart is a place of love
When Allah (subhanahu wa ta’ala) places a seal on their hearts, they are incapable of loving what they should. They hate the things that deserve love. They are supposed to love the believer, and they start hating the believer. They are supposed to love truth, they develop a hatred for the truth. They are supposed to love justice, and they develop a hatred for justice.
Heart includes rahmah
When the heart is sealed, rahmah is gone. These people can then say and do the most cruel things.
Heart is a place of gratitude
When the heart is sealed, they feel no gratitude. They feel no reason to thank anyone. They feel entitled to everything.
Heart is a place of fear
When the heart is sealed, they feel no fear for the things they do. They fear no consequences.
Heart is a place of hope
When the heart is sealed, these people are completely hopeless. They have no hopes in the akhirah. They have no hopes in the good of anyone else. They don’t even hope better for themselves. They consider everything fatalistic.
Heart is a place of guilt
When we do something wrong, Allah (subhanahu wa ta’ala) put a fitrah in the human being, when we feel bad. When the heart is sealed, one can do the most horrible things and still be proud of them. Shaitan beautifies their deeds for them.
Heart is a place of shame
When the heart is sealed, these people have no shame left. They are lewd, vile and vulgar in their speech, in their clothing etc. and it doesn’t matter to them. They will beautify for themselves what Allah (subhanahu wa ta’ala) made it as ugly in the fitrah of the human being.
Heart is a place for a sense of responsibility
When the heart is sealed, one doesn’t feel any responsibility towards anyone else including spouse, parents, children, neighbors etc.
Heart is a place of dignity
When the heart is sealed there is no sense of dignity or respect left for yourself or for anyone else.
When Allah (subhanahu wa ta’ala) says he has sealed their hearts, it is not a small thing. Everything good that comes from the heart, the entire fitrah of the human being, is gone.