More then this (Brethren) ye see the Thessalonians are elected: yet he prays for them, Making mention (sayeth he) of you in our prayers. And for this same cause; knowing that ye are elected. Mark this. The election of God, that sure ground and foundation of life and salvation, prejudges not prayer. Therefore, say not, I am elected, my salvation cannot fail, saved must I be therefore, what needs me to pray myself, or cause any other pray for me? No, by the contrary, say, I am elected, therefore, I will pray: ye are the elect, therefore, I will pray for you: that is Paul’s reason.
For, as salvation, and life is predestinate and appointed by God, so are the means of salvation appointed by God, which thou must use, if ever thou wouldst attain to life, notwithstanding of thy election. And among all the rest of the means, Prayer is one: thou who art chosen to life, prayers is a mean to thee, to be used before thou come to life: Pray must thou, and others must pray for thee, or else, thou was never chosen to life.
There was never man chosen to life from all eternity; but the Lord appointed that he should use prayer; also God ordained that he should live in holiness, and work good works, which is an other mean must be used. Ephes. 2. 10. For, if prayer be not used, if he live not holy, if he live without love, without charity and good works, if he continue so to the end, he shall find that he was never chosen.
Robert Rollock, Lectures upon the first and second Epistles of Paul to the Thessalonians (Edinburgh: Robert Charteris, 1606), pp 16-17.