
67 S.E.2d 285 (1951)
234 N.C. 394
McLAWHON et al.
v.
BRILEY.
No. 306.
Supreme Court of North Carolina.
October 31, 1951.
*286 Albion Dunn, Greenville, for plaintiffs, appellants.
James & Speight, Greenville, for defendant, appellee.
DEVIN, Chief Justice.
The plaintiffs challenge the validity of the verdict and judgment below chiefly on the ground that the court permitted oral testimony from the defendant as to the terms of the contract inconsistent with the written receipt signed by defendant when the machinery described in the complaint was delivered to him.
It is a well settled rule that when parties have reduced their agreement to writing parol evidence is not admissible to contradict it for the reason that the written memorial is the best evidence of what the parties have agreed to. Evans v. Freeman, 142 N.C. 61, 54 S.E. 847. Prior negotiations are deemed merged in the written contract of the parties, and the law excludes oral testimony which tends to contradict, vary or add to the terms as expressed in the writing. American Potato Co. v. Jenette Bros., 172 N.C. 1, 89 S.E. 791. Under this rule parol testimony as to communications or declarations of the parties at or before the execution of a written contract will not be received for the purpose of substituting a different agreement for the one expressed in the writing. Potter v. National Supply Co., 230 N.C. 1, (9), 51 S.E.2d 908. But this rule applies only when the entire contract has been reduced to writing, for if merely a part has been written and the remainder rests in parol, it is competent to establish the latter by oral evidence, provided it does not contradict what has been written. Evans v. Freeman, supra.
Here, the defendant testified the plaintiffs orally contracted to sell and deliver to them certain farm machinery with necessary equipment; that the contract was entire and indivisible since a part of the machinery contracted for would be practically useless without the remainder; that when a portion of the machinery and equipment was delivered he merely signed a receipt showing that which was actually delivered.
We think the rule invoked by plaintiffs is inapplicable to the facts here shown, and that the evidence to which plaintiffs' *287 exception was directed was competent. The issues submitted to the jury were those arising on the pleadings and testimony.
Defendant's contention that the plaintiffs' inability to deliver the other equipment contracted for and essential for use with the tractor absolved him from obligation to accept and pay for the parts delivered, was upheld by the jury.
Where the contract is entire the obligation imposed stands or falls as whole, Pure Oil Co. of the Carolinas v. Baars, 224 N.C. 612, 31 S.E.2d 854, and defendant would have the right to refuse to accept delivery of a part of the machinery contracted for as a compliance with the entire contract. Hence, the defendant upon return of the parts received would be entitled to recover the partial payments made on the contract, as found by the jury.
We have examined the other exceptions noted and brought forward in plaintiffs' assignments of error and find they afford insufficient ground to disturb the result.
No error.
