In The Name of Allaah, The Most Merciful, The Bestower of Mercy
Allaah [The Most High] said in Surah Al-Mulk’ Aayaat 13-14:
وَأَسِرُّواْ قَوۡلَكُمۡ أَوِ ٱجۡهَرُواْ بِهِۦۤۖ إِنَّهُ ۥ عَلِيمُۢ بِذَاتِ ٱلصُّدُورِ
And whether you keep your talk secret or disclose it, verily, He is the All-Knower of what is in the breasts (of men). Should not He Who has created know? And He is the Most Kind and Courteous (to His slaves) All-Aware (of everything). [67:13-14]
Few Reminders from the above Ayah:
This [i.e. the above Ayah] is from the highest degree of affirmation [or confirmation], for indeed it has to be [the case that] the Creator knows His creatures. Therefore, if you affirm that indeed Allaah is your Creator and the Creator of your hearts and what they contain [or all that is conceal in the hearts], then how can [anything] be hidden from Him when [it is the case] that Allaah created the hearts?!
And the statement [بِذَاتِ الصُّدُورِ – what is in the breasts (of men)] includes what the breasts contain of beliefs, intents, love and hate.
[Source: (Badaa’i At-Tafseer Al-Jaami Limaa Fassarahu Al-Imaam Ibnul Qayyim). page 173). Abridged & Slightly Paraphrased]