Is it obligatory for a person to recite the adhkar with an audible voice, or is it sufficient for him to utter them with his tongue?

The questioner : Is it obligatory for a person to recite the adhkar with an audible voice, or is it sufficient for him to utter them with his tongue?

The Shaykh : It is sufficient for him to utter them with his tongue, as long as he pronounces the letters; however, merely passing them through the heart is not sufficient.
But there is a matter here, which is: raising the voice in dhikr after the obligatory prayers is a recommended practice (sunnah), as Abdullah ibn Abbas (may Allah be pleased with him and his father) said: . Many people nowadays have neglected this sunnah, so you will not find them raising their voices with it. But the truth is more worthy of being followed; raising the voice is better, except if there is a man next to you making up what he missed from the prayer, and you fear that if you raise your voice you will disturb him. In that case, do not do it; do not raise your voice.