Unto whom David said, If thou passest on with me, then thou shalt be a burden unto me:

and David saith to him, 'If thou hast passed on with me then thou hast been on me for a burden,

David said to him, If you go on with me, you will be a trouble to me:

Then thou shalt be a burden unto me - It appears that Hushai was not a warrior, but was a wise, prudent, and discreet man, who could well serve David by gaining him intelligence of Absalom's conspiracy; and he directs him to form a strict confederacy with the priests Zadok and Abiathar, and to make use of their sons as couriers between Jerusalem and David's place of retreat.

Unto whom David said,.... After he had heard what he had to say, and what tidings he brought:
and if thou passest on with me; in his march and flight:
then thou shalt be a burden to me; being to be maintained by him; and David having but scanty provisions, and so could not receive useless persons, as Hushai might be, perhaps an old man, that could be of no service to him, and unfit for travelling, and so would rather be an hinderance than an help unto him.