अन्यतरामेव वर्तनीँ संस्करोति हीयतेऽन्यतरा स यथैकपाद्व्रजन्नथो वैकेन चक्रेण वर्तमानो रिष्यत्येवमस्य यज्ञो रिष्यति यज्ञँ रिष्यन्तं यजमानोऽनुरिष्यति स इष्ट्वा पापीयान्भवति ॥ ३ ॥
In plain words
If only one path is refined, the other is neglected. Just as a traveler moving on one foot or a carriage rolling on a single wheel stumbles, so too does this sacrifice fail. As the sacrifice fails, the patron of the sacrifice fails along with it, and having performed the rite, he falls into ruin.
Close to the Sanskrit
If one refines only one path, the other path is left deficient. Just as one walking on one foot, or moving with a single wheel, comes to grief, thus his sacrifice suffers ruin; following the sacrifice suffering ruin, the sacrificer suffers ruin, and having sacrificed, he becomes worse off.