The heart of the matter is the matter of the heart

Duty must be cordial and hearty for with the heart man believeth unto righteousness. The matter must swim not in the head or understanding, but it must be in the heart - not just persuaded but affectionately persuaded, loving and liking the thing - a heart business, a soul business, yea, not a business in the outer courts of the affections but in the flower of the affections and in the innermost cabinet of the soul where Christ is formed. Christ as the bridegroom will have the heart or nothing, love or nothing, marriage love which goeth from heart to heart, love of espousals or nothing.

William Guthrie, The Christian's Great Interest