Sadr (breast) is connected with Islam (Sūra 39:23); qalb (heart) is the seat of īmān (faith) (Sūra 49:7; 16:106); fuad (heart) is connected with marifa (gnosis) (Sūra 53:11); and lubb (innermost heart) is the seat of tauhīd (Sūra 3:190).