The Righteous Necessity of the Imputation of Christ's Active Obedience For Eternal Life

More (see HERE) from Eighteen Sermons on Romans 8:1-4, pp 590-91 ( 1672) by Thomas Jacomb who makes the case for the necessity of the active obedience of Christ imputed to the believer in justification - a necessity, he argues - extending beyond the justification which comes to the sinner upon first believing in Christ but further unto the believer's 'title to eternal life.'

"And I desire the words may be well observed; 'tis not said that the righteousness of the Law might be endured, suffered, or undergone by us, as if it did relate to the penalty of the Law; but that the righteousness of the Law might be fulfilled in us, which surely most properly must relate to the doing part of the Law: doth he *fulfil who suffers? that's very harsh. To say that one of the things that have been spoken of was or is sufficient viz. the undergoing of the punishment without the doing of the duty, and that therefore the imputation of Christ's death and sufferings is enough: I say for any to assert this, they do (in my thoughts ) offer some violence to the Text in hand, which tells us the righteousness, the whole righteousness of the Law was to be and is fulfilled in believers. 

"3. 'Tis urged thirdly, 'tis necessary not only in respect of the Law, but of ourselves also that Christ's active Obedience should be imputed, inasmuch as our righteousness and title to eternal life do indispensably depend upon it. The Law is the measure and standard of righteousness, let that be fulfilled and a person is righteous, otherwise not; without this none can stand before the great God as being such. Well then, the Sinner himself being altogether unable thus to fulfil the Law thereby to be made righteous; Christ's fulfilling of it must be imputed to him in order to righteousness. Guilt and righteousness do both carry in them a reference to the holy Law; when that is broken, 'tis guilt; when that is kept, 'tis righteousness: therefore as, supposing that Law had not been transgressed, we had not been guilty, so unless that Law be fully conform'd to, we cannot be *righteous. Now where shall we find this full conformity to the Law but in Christ? and what will that in Christ avail us if it be not imputed and made over to us? So as to eternal Life, unto which without fulfilling the Law we can have no claim or title: For the old Law-condition or Covenant being yet in force, do and live, (Lev. 18:5; Rom. 10:5; Gal. 3:12; Luke 10:28); unless this Condition be performed we cannot hope for life. True indeed, under the Covenant of Grace God accepts of what is done by the Surety, and he doth not expect of the Sinner in his own person the perfect obeying of the Law as a condition of life, but yet he will have the thing done either by or for the Sinner, either by himself or by his Surety, or else no life: doth not this then evince the necessity of the imputation of Christ's active Obedience?" [emphasis in the original]