Psalms 145:18

In truth— Or, in fidelity, or constancy. This fidelity or constancy may be applied either to the person praying, or to the prayer itself. If to the person, it then signifies his firm adherence to God, and constancy in serving him, without applying himself to any indirect means to obtain what he prays for; but waiting only on God to receive it from him in his good time. If to the prayer itself, it signifies the constancy of his address, in not giving over his petitions when they are not immediately granted, but enforcing them with importunity; and it is to the union of these two conditions that the promise is here made, that the prayer so qualified shall certainly, in God's due time, be answered by him.