Kathasaritsagara 3.6.100

3.6.100

tad evaṃ devi devānām api santi na siddhayaḥ /
herambe 'narcite tasmāt pūjayainaṃ varārthinī //

But from the body of Kártikeya, when struck by the thunderbolt of Indra, there sprang two sons called Śákha and Viśákha, both of incomparable might. Then Śiva, came to his offspring Kártikeya, who exceeded Indra in might, and forbade him and his two sons to fight, and rebuked him in the following words: " Thou wast born in order that thou mightest slay Táraka and protect the realm of Indra, therefore do thy own duty." Then Indra was delighted and immediately bowed before him, and commenced the ceremony of consecrating by ablutions Kártikeya as general of his forces. But when he himself lifted the pitcher for that purpose, his arm became stiff, wherefore he was despondent, but Śiva said to him; " Thou didst not worship the elephant-faced god, when thou desiredst a general; it was for this reason that thou hast met with this obstacle, therefore adore him now." Indra,when he heard that, did so, and his arm was set free, and he duly performed the joyful ceremony of consecrating the general. And not long after, the general slew the Asura Táraka, and the gods rejoiced at having accomplished their object, and Gaurí at having obtained a son. So, princess, you see even the gods are not successful without honouring Ganeśa, therefore adore him when you desire a blessing.