Charles H. Spurgeon on Psalms 119:36

Incline my heart. In the former verses David had asked understanding and direction to know the Lord's will; now he asketh an inclination of heart to do the Lord's will. The understanding needs not only to be enlightened, but the will to be moved and changed. Man's heart is of its own accord averse from God and holiness, even then when the wit is most refined, and the understanding is stocked and stored with high notions about it: therefore David doth not only say, "Give me understanding, "but, "Incline my heart." We can be worldly of ourselves, but we cannot be holy and heavenly of ourselves; that must be asked of him who is the Father of lights, from whom cometh down every good and perfect gift. They that plead for the power of nature, shut out the use of prayer. But Austin hath said well, Naturn vera confessione non falsa defersione opus habet:we need rather to confess our weakness, than defend our strength. Thus doth David, and so will every broken hearted Christian that hath had an experience of the inclinations of his own soul, he will come to God, and say, Incline my heart unto thy testimonies, and not to covetousness. Thomas Manton.