The Prophet (peace and blessings be upon him) said:
"When any of you invites his brother, he should accept the invitation, whether it is a wedding feast (walimah) or some other occasion like it."
Hadith Referenceصحیح الجامع الصغیر / حرف الألف / 529
Hadith Gradingالألبانی:صحيح
Hadith Takhrij[حم د] عن ابن عمر. مختصر مسلم ٨٢٥، آداب الزفاف ٧٢: م.