Is the testimony of one partner against the other admissible?

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The testimony of one partner against his associate is accepted. This is the view of Ahmad and the majority of scholars. The evidence for this is the command in the Almighty's saying: "O you who have believed, be persistently firm in justice, witnesses for Allah, even if it be against yourselves or parents and relatives" (Quran 4:135). If the testimony were not accepted, the command to give it would be meaningless. Furthermore, testimony is rejected due to suspicion of conferring benefit, whereas there is no suspicion of conferring benefit when testifying against a partner; hence, it must be accepted, similar to the testimony of a stranger, or even more so. Since one's testimony for himself is rejected due to suspicion of conferring personal benefit, his admission against himself is accepted.